TCSH(1) TCSH(1) NNAAMMEE tcsh - C shell with file name completion and command line editing SSYYNNOOPPSSIISS ttccsshh [--bbccddeeffFFiimmnnqqssttvvVVxxXX] [--DDnnaammee[==vvaalluuee]] [arg ...] ttccsshh --ll DDEESSCCRRIIPPTTIIOONN _t_c_s_h is an enhanced but completely compatible version of the Berkeley UNIX C shell, _c_s_h(1). It is a command language interpreter usable both as an interactive login shell and a shell script command processor. It includes a command-line editor (see TThhee ccoommmmaanndd--lliinnee eeddiittoorr), pro- grammable word completion (see CCoommpplleettiioonn aanndd lliissttiinngg), spelling cor- rection (see SSppeelllliinngg ccoorrrreeccttiioonn), a history mechanism (see HHiissttoorryy ssuubbssttiittuuttiioonn), job control (see JJoobbss) and a C-like syntax. The NNEEWW FFEEAATTUURREESS section describes major enhancements of _t_c_s_h over _c_s_h(1). Throughout this manual, features of _t_c_s_h not found in most _c_s_h(1) implementations (specifically, the 4.4BSD _c_s_h) are labeled with `(+)', and features which are present in _c_s_h(1) but not usually documented are labeled with `(u)'. AArrgguummeenntt lliisstt pprroocceessssiinngg If the first argument (argument 0) to the shell is `-' then it is a login shell. A login shell can be also specified by invoking the shell with the --ll flag as the only argument. The rest of the flag arguments are interpreted as follows: --bb Forces a ``break'' from option processing, causing any further shell arguments to be treated as non-option arguments. The remain- ing arguments will not be interpreted as shell options. This may be used to pass options to a shell script without confusion or pos- sible subterfuge. The shell will not run a set-user ID script without this option. --cc Commands are read from the following argument (which must be present, and must be a single argument), stored in the ccoommmmaanndd shell variable for reference, and executed. Any remaining argu- ments are placed in the aarrggvv shell variable. --dd The shell loads the directory stack from _~_/_._c_s_h_d_i_r_s as described under SSttaarrttuupp aanndd sshhuuttddoowwnn, whether or not it is a login shell. (+) --DD_n_a_m_e[=_v_a_l_u_e] Sets the environment variable _n_a_m_e to _v_a_l_u_e. (Domain/OS only) (+) --ee The shell exits if any invoked command terminates abnormally or yields a non-zero exit status. --ff The shell ignores _~_/_._t_c_s_h_r_c, and thus starts faster. --FF The shell uses _f_o_r_k(2) instead of _v_f_o_r_k(2) to spawn processes. (Convex/OS only) (+) --ii The shell is interactive and prompts for its top-level input, even if it appears to not be a terminal. Shells are interactive without this option if their inputs and outputs are terminals. --ll The shell is a login shell. Applicable only if --ll is the only flag specified. --mm The shell loads _~_/_._t_c_s_h_r_c even if it does not belong to the effec- tive user. Newer versions of _s_u(1) can pass --mm to the shell. (+) --nn The shell parses commands but does not execute them. This aids in debugging shell scripts. --qq The shell accepts SIGQUIT (see SSiiggnnaall hhaannddlliinngg) and behaves when it is used under a debugger. Job control is disabled. (u) --ss Command input is taken from the standard input. --tt The shell reads and executes a single line of input. A `\' may be used to escape the newline at the end of this line and continue onto another line. --vv Sets the vveerrbboossee shell variable, so that command input is echoed after history substitution. --xx Sets the eecchhoo shell variable, so that commands are echoed immedi- ately before execution. --VV Sets the vveerrbboossee shell variable even before executing _~_/_._t_c_s_h_r_c. --XX Is to --xx as --VV is to --vv. ----hheellpp Print a help message on the standard output and exit. (+) ----vveerrssiioonn Print the version/platform/compilation options on the standard out- put and exit. This information is also contained in the vveerrssiioonn shell variable. (+) After processing of flag arguments, if arguments remain but none of the --cc, --ii, --ss, or --tt options were given, the first argument is taken as the name of a file of commands, or ``script'', to be executed. The shell opens this file and saves its name for possible resubstitution by `$0'. Because many systems use either the standard version 6 or ver- sion 7 shells whose shell scripts are not compatible with this shell, the shell uses such a `standard' shell to execute a script whose first character is not a `#', i.e., that does not start with a comment. Remaining arguments are placed in the aarrggvv shell variable. SSttaarrttuupp aanndd sshhuuttddoowwnn A login shell begins by executing commands from the system files _/_e_t_c_/_c_s_h_._c_s_h_r_c and _/_e_t_c_/_c_s_h_._l_o_g_i_n. It then executes commands from files in the user's hhoommee directory: first _~_/_._t_c_s_h_r_c (+) or, if _~_/_._t_c_s_h_r_c is not found, _~_/_._c_s_h_r_c, then _~_/_._h_i_s_t_o_r_y (or the value of the hhiissttffiillee shell variable), then _~_/_._l_o_g_i_n, and finally _~_/_._c_s_h_d_i_r_s (or the value of the ddiirrssffiillee shell variable) (+). The shell may read _/_e_t_c_/_c_s_h_._l_o_g_i_n before instead of after _/_e_t_c_/_c_s_h_._c_s_h_r_c, and _~_/_._l_o_g_i_n before instead of after _~_/_._t_c_s_h_r_c or _~_/_._c_s_h_r_c and _~_/_._h_i_s_t_o_r_y, if so compiled; see the vveerrssiioonn shell variable. (+) Non-login shells read only _/_e_t_c_/_c_s_h_._c_s_h_r_c and _~_/_._t_c_s_h_r_c or _~_/_._c_s_h_r_c on startup. For examples of startup files, please consult _h_t_t_p_:_/_/_t_c_s_h_r_c_._s_o_u_r_c_e_- _f_o_r_g_e_._n_e_t. Commands like _s_t_t_y(1) and _t_s_e_t(1), which need be run only once per login, usually go in one's _~_/_._l_o_g_i_n file. Users who need to use the same set of files with both _c_s_h(1) and _t_c_s_h can have only a _~_/_._c_s_h_r_c which checks for the existence of the ttccsshh shell variable (q.v.) before using _t_c_s_h-specific commands, or can have both a _~_/_._c_s_h_r_c and a _~_/_._t_c_s_h_r_c which _s_o_u_r_c_es (see the builtin command) _~_/_._c_s_h_r_c. The rest of this manual uses `_~_/_._t_c_s_h_r_c' to mean `_~_/_._t_c_s_h_r_c or, if _~_/_._t_c_s_h_r_c is not found, _~_/_._c_s_h_r_c'. In the normal case, the shell begins reading commands from the termi- nal, prompting with `> '. (Processing of arguments and the use of the shell to process files containing command scripts are described later.) The shell repeatedly reads a line of command input, breaks it into words, places it on the command history list, parses it and executes each command in the line. One can log out by typing `^D' on an empty line, `logout' or `login' or via the shell's autologout mechanism (see the aauuttoollooggoouutt shell vari- able). When a login shell terminates it sets the llooggoouutt shell variable to `normal' or `automatic' as appropriate, then executes commands from the files _/_e_t_c_/_c_s_h_._l_o_g_o_u_t and _~_/_._l_o_g_o_u_t. The shell may drop DTR on logout if so compiled; see the vveerrssiioonn shell variable. The names of the system login and logout files vary from system to sys- tem for compatibility with different _c_s_h(1) variants; see FFIILLEESS. EEddiittiinngg We first describe TThhee ccoommmmaanndd--lliinnee eeddiittoorr. The CCoommpplleettiioonn aanndd lliissttiinngg and SSppeelllliinngg ccoorrrreeccttiioonn sections describe two sets of functionality that are implemented as editor commands but which deserve their own treatment. Finally, EEddiittoorr ccoommmmaannddss lists and describes the editor commands specific to the shell and their default bindings. TThhee ccoommmmaanndd--lliinnee eeddiittoorr ((++)) Command-line input can be edited using key sequences much like those used in GNU Emacs or _v_i(1). The editor is active only when the eeddiitt shell variable is set, which it is by default in interactive shells. The _b_i_n_d_k_e_y builtin can display and change key bindings. Emacs-style key bindings are used by default (unless the shell was compiled other- wise; see the vveerrssiioonn shell variable), but _b_i_n_d_k_e_y can change the key bindings to _v_i-style bindings en masse. The shell always binds the arrow keys (as defined in the TTEERRMMCCAAPP envi- ronment variable) to down _d_o_w_n_-_h_i_s_t_o_r_y up _u_p_-_h_i_s_t_o_r_y left _b_a_c_k_w_a_r_d_-_c_h_a_r right _f_o_r_w_a_r_d_-_c_h_a_r unless doing so would alter another single-character binding. One can set the arrow key escape sequences to the empty string with _s_e_t_t_c to prevent these bindings. The ANSI/VT100 sequences for arrow keys are always bound. Other key bindings are, for the most part, what Emacs and _v_i(1) users would expect and can easily be displayed by _b_i_n_d_k_e_y, so there is no need to list them here. Likewise, _b_i_n_d_k_e_y can list the editor commands with a short description of each. Note that editor commands do not have the same notion of a ``word'' as does the shell. The editor delimits words with any non-alphanumeric characters not in the shell variable wwoorrddcchhaarrss, while the shell recog- nizes only whitespace and some of the characters with special meanings to it, listed under LLeexxiiccaall ssttrruuccttuurree. CCoommpplleettiioonn aanndd lliissttiinngg ((++)) The shell is often able to complete words when given a unique abbrevia- tion. Type part of a word (for example `ls /usr/lost') and hit the tab key to run the _c_o_m_p_l_e_t_e_-_w_o_r_d editor command. The shell completes the filename `/usr/lost' to `/usr/lost+found/', replacing the incomplete word with the complete word in the input buffer. (Note the terminal `/'; completion adds a `/' to the end of completed directories and a space to the end of other completed words, to speed typing and provide a visual indicator of successful completion. The aaddddssuuffffiixx shell vari- able can be unset to prevent this.) If no match is found (perhaps `/usr/lost+found' doesn't exist), the terminal bell rings. If the word is already complete (perhaps there is a `/usr/lost' on your system, or perhaps you were thinking too far ahead and typed the whole thing) a `/' or space is added to the end if it isn't already there. Completion works anywhere in the line, not at just the end; completed text pushes the rest of the line to the right. Completion in the mid- dle of a word often results in leftover characters to the right of the cursor that need to be deleted. Commands and variables can be completed in much the same way. For example, typing `em[tab]' would complete `em' to `emacs' if _e_m_a_c_s were the only command on your system beginning with `em'. Completion can find a command in any directory in ppaatthh or if given a full pathname. Typing `echo $ar[tab]' would complete `$ar' to `$argv' if no other variable began with `ar'. The shell parses the input buffer to determine whether the word you want to complete should be completed as a filename, command or vari- able. The first word in the buffer and the first word following `;', `|', `|&', `&&' or `||' is considered to be a command. A word begin- ning with `$' is considered to be a variable. Anything else is a file- name. An empty line is `completed' as a filename. You can list the possible completions of a word at any time by typing `^D' to run the _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_l_i_s_t_-_o_r_-_e_o_f editor command. The shell lists the possible completions using the _l_s_-_F builtin (q.v.) and re- prints the prompt and unfinished command line, for example: > ls /usr/l[^D] lbin/ lib/ local/ lost+found/ > ls /usr/l If the aauuttoolliisstt shell variable is set, the shell lists the remaining choices (if any) whenever completion fails: > set autolist > nm /usr/lib/libt[tab] libtermcap.a@ libtermlib.a@ > nm /usr/lib/libterm If aauuttoolliisstt is set to `ambiguous', choices are listed only when comple- tion fails and adds no new characters to the word being completed. A filename to be completed can contain variables, your own or others' home directories abbreviated with `~' (see FFiilleennaammee ssuubbssttiittuuttiioonn) and directory stack entries abbreviated with `=' (see DDiirreeccttoorryy ssttaacckk ssuubb-- ssttiittuuttiioonn). For example, > ls ~k[^D] kahn kas kellogg > ls ~ke[tab] > ls ~kellogg/ or > set local = /usr/local > ls $lo[tab] > ls $local/[^D] bin/ etc/ lib/ man/ src/ > ls $local/ Note that variables can also be expanded explicitly with the _e_x_p_a_n_d_- _v_a_r_i_a_b_l_e_s editor command. _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_l_i_s_t_-_o_r_-_e_o_f lists at only the end of the line; in the middle of a line it deletes the character under the cursor and on an empty line it logs one out or, if iiggnnoorreeeeooff is set, does nothing. `M-^D', bound to the editor command _l_i_s_t_-_c_h_o_i_c_e_s, lists completion pos- sibilities anywhere on a line, and _l_i_s_t_-_c_h_o_i_c_e_s (or any one of the related editor commands that do or don't delete, list and/or log out, listed under _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_l_i_s_t_-_o_r_-_e_o_f) can be bound to `^D' with the _b_i_n_d_k_e_y builtin command if so desired. The _c_o_m_p_l_e_t_e_-_w_o_r_d_-_f_w_d and _c_o_m_p_l_e_t_e_-_w_o_r_d_-_b_a_c_k editor commands (not bound to any keys by default) can be used to cycle up and down through the list of possible completions, replacing the current word with the next or previous word in the list. The shell variable ffiiggnnoorree can be set to a list of suffixes to be ignored by completion. Consider the following: > ls Makefile condiments.h~ main.o side.c README main.c meal side.o condiments.h main.c~ > set fignore = (.o \~) > emacs ma[^D] main.c main.c~ main.o > emacs ma[tab] > emacs main.c `main.c~' and `main.o' are ignored by completion (but not listing), because they end in suffixes in ffiiggnnoorree. Note that a `\' was needed in front of `~' to prevent it from being expanded to hhoommee as described under FFiilleennaammee ssuubbssttiittuuttiioonn. ffiiggnnoorree is ignored if only one completion is possible. If the ccoommpplleettee shell variable is set to `enhance', completion 1) ignores case and 2) considers periods, hyphens and underscores (`.', `-' and `_') to be word separators and hyphens and underscores to be equivalent. If you had the following files comp.lang.c comp.lang.perl comp.std.c++ comp.lang.c++ comp.std.c and typed `mail -f c.l.c[tab]', it would be completed to `mail -f comp.lang.c', and ^D would list `comp.lang.c' and `comp.lang.c++'. `mail -f c..c++[^D]' would list `comp.lang.c++' and `comp.std.c++'. Typing `rm a--file[^D]' in the following directory A_silly_file a-hyphenated-file another_silly_file would list all three files, because case is ignored and hyphens and underscores are equivalent. Periods, however, are not equivalent to hyphens or underscores. Completion and listing are affected by several other shell variables: rreecceexxaacctt can be set to complete on the shortest possible unique match, even if more typing might result in a longer match: > ls fodder foo food foonly > set recexact > rm fo[tab] just beeps, because `fo' could expand to `fod' or `foo', but if we type another `o', > rm foo[tab] > rm foo the completion completes on `foo', even though `food' and `foonly' also match. aauuttooeexxppaanndd can be set to run the _e_x_p_a_n_d_-_h_i_s_t_o_r_y editor command before each completion attempt, aauuttooccoorrrreecctt can be set to spelling-cor- rect the word to be completed (see SSppeelllliinngg ccoorrrreeccttiioonn) before each completion attempt and ccoorrrreecctt can be set to complete commands automat- ically after one hits `return'. mmaattcchhbbeeeepp can be set to make comple- tion beep or not beep in a variety of situations, and nnoobbeeeepp can be set to never beep at all. nnoossttaatt can be set to a list of directories and/or patterns that match directories to prevent the completion mecha- nism from _s_t_a_t(2)ing those directories. lliissttmmaaxx and lliissttmmaaxxrroowwss can be set to limit the number of items and rows (respectively) that are listed without asking first. rreeccooggnniizzee__oonnllyy__eexxeeccuuttaabblleess can be set to make the shell list only executables when listing commands, but it is quite slow. Finally, the _c_o_m_p_l_e_t_e builtin command can be used to tell the shell how to complete words other than filenames, commands and variables. Com- pletion and listing do not work on glob-patterns (see FFiilleennaammee ssuubbssttii-- ttuuttiioonn), but the _l_i_s_t_-_g_l_o_b and _e_x_p_a_n_d_-_g_l_o_b editor commands perform equivalent functions for glob-patterns. SSppeelllliinngg ccoorrrreeccttiioonn ((++)) The shell can sometimes correct the spelling of filenames, commands and variable names as well as completing and listing them. Individual words can be spelling-corrected with the _s_p_e_l_l_-_w_o_r_d editor command (usually bound to M-s and M-S) and the entire input buffer with _s_p_e_l_l_-_l_i_n_e (usually bound to M-$). The ccoorrrreecctt shell variable can be set to `cmd' to correct the command name or `all' to correct the entire line each time return is typed, and aauuttooccoorrrreecctt can be set to correct the word to be completed before each completion attempt. When spelling correction is invoked in any of these ways and the shell thinks that any part of the command line is misspelled, it prompts with the corrected line: > set correct = cmd > lz /usr/bin CORRECT>ls /usr/bin (y|n|e|a)? One can answer `y' or space to execute the corrected line, `e' to leave the uncorrected command in the input buffer, `a' to abort the command as if `^C' had been hit, and anything else to execute the original line unchanged. Spelling correction recognizes user-defined completions (see the _c_o_m_- _p_l_e_t_e builtin command). If an input word in a position for which a completion is defined resembles a word in the completion list, spelling correction registers a misspelling and suggests the latter word as a correction. However, if the input word does not match any of the pos- sible completions for that position, spelling correction does not reg- ister a misspelling. Like completion, spelling correction works anywhere in the line, push- ing the rest of the line to the right and possibly leaving extra char- acters to the right of the cursor. Beware: spelling correction is not guaranteed to work the way one intends, and is provided mostly as an experimental feature. Sugges- tions and improvements are welcome. EEddiittoorr ccoommmmaannddss ((++)) `bindkey' lists key bindings and `bindkey -l' lists and briefly describes editor commands. Only new or especially interesting editor commands are described here. See _e_m_a_c_s(1) and _v_i(1) for descriptions of each editor's key bindings. The character or characters to which each command is bound by default is given in parentheses. `^_c_h_a_r_a_c_t_e_r' means a control character and `M-_c_h_a_r_a_c_t_e_r' a meta character, typed as escape-_c_h_a_r_a_c_t_e_r on terminals without a meta key. Case counts, but commands that are bound to let- ters by default are bound to both lower- and uppercase letters for con- venience. ccoommpplleettee--wwoorrdd (tab) Completes a word as described under CCoommpplleettiioonn aanndd lliissttiinngg. ccoommpplleettee--wwoorrdd--bbaacckk (not bound) Like _c_o_m_p_l_e_t_e_-_w_o_r_d_-_f_w_d, but steps up from the end of the list. ccoommpplleettee--wwoorrdd--ffwwdd (not bound) Replaces the current word with the first word in the list of possible completions. May be repeated to step down through the list. At the end of the list, beeps and reverts to the incom- plete word. ccoommpplleettee--wwoorrdd--rraaww (^X-tab) Like _c_o_m_p_l_e_t_e_-_w_o_r_d, but ignores user-defined completions. ccooppyy--pprreevv--wwoorrdd (M-^_) Copies the previous word in the current line into the input buffer. See also _i_n_s_e_r_t_-_l_a_s_t_-_w_o_r_d. ddaabbbbrreevv--eexxppaanndd (M-/) Expands the current word to the most recent preceding one for which the current is a leading substring, wrapping around the history list (once) if necessary. Repeating _d_a_b_b_r_e_v_-_e_x_p_a_n_d without any intervening typing changes to the next previous word etc., skipping identical matches much like _h_i_s_t_o_r_y_-_s_e_a_r_c_h_- _b_a_c_k_w_a_r_d does. ddeelleettee--cchhaarr (not bound) Deletes the character under the cursor. See also _d_e_l_e_t_e_-_c_h_a_r_- _o_r_-_l_i_s_t_-_o_r_-_e_o_f. ddeelleettee--cchhaarr--oorr--eeooff (not bound) Does _d_e_l_e_t_e_-_c_h_a_r if there is a character under the cursor or _e_n_d_-_o_f_-_f_i_l_e on an empty line. See also _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_l_i_s_t_-_o_r_- _e_o_f. ddeelleettee--cchhaarr--oorr--lliisstt (not bound) Does _d_e_l_e_t_e_-_c_h_a_r if there is a character under the cursor or _l_i_s_t_-_c_h_o_i_c_e_s at the end of the line. See also _d_e_l_e_t_e_-_c_h_a_r_-_o_r_- _l_i_s_t_-_o_r_-_e_o_f. ddeelleettee--cchhaarr--oorr--lliisstt--oorr--eeooff (^D) Does _d_e_l_e_t_e_-_c_h_a_r if there is a character under the cursor, _l_i_s_t_-_c_h_o_i_c_e_s at the end of the line or _e_n_d_-_o_f_-_f_i_l_e on an empty line. See also those three commands, each of which does only a single action, and _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_e_o_f, _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_l_i_s_t and _l_i_s_t_-_o_r_-_e_o_f, each of which does a different two out of the three. ddoowwnn--hhiissttoorryy (down-arrow, ^N) Like _u_p_-_h_i_s_t_o_r_y, but steps down, stopping at the original input line. eenndd--ooff--ffiillee (not bound) Signals an end of file, causing the shell to exit unless the iiggnnoorreeeeooff shell variable (q.v.) is set to prevent this. See also _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_l_i_s_t_-_o_r_-_e_o_f. eexxppaanndd--hhiissttoorryy (M-space) Expands history substitutions in the current word. See HHiissttoorryy ssuubbssttiittuuttiioonn. See also _m_a_g_i_c_-_s_p_a_c_e, _t_o_g_g_l_e_-_l_i_t_e_r_a_l_-_h_i_s_t_o_r_y and the aauuttooeexxppaanndd shell variable. eexxppaanndd--gglloobb (^X-*) Expands the glob-pattern to the left of the cursor. See FFiillee-- nnaammee ssuubbssttiittuuttiioonn. eexxppaanndd--lliinnee (not bound) Like _e_x_p_a_n_d_-_h_i_s_t_o_r_y, but expands history substitutions in each word in the input buffer, eexxppaanndd--vvaarriiaabblleess (^X-$) Expands the variable to the left of the cursor. See VVaarriiaabbllee ssuubbssttiittuuttiioonn. hhiissttoorryy--sseeaarrcchh--bbaacckkwwaarrdd (M-p, M-P) Searches backwards through the history list for a command beginning with the current contents of the input buffer up to the cursor and copies it into the input buffer. The search string may be a glob-pattern (see FFiilleennaammee ssuubbssttiittuuttiioonn) con- taining `*', `?', `[]' or `{}'. _u_p_-_h_i_s_t_o_r_y and _d_o_w_n_-_h_i_s_t_o_r_y will proceed from the appropriate point in the history list. Emacs mode only. See also _h_i_s_t_o_r_y_-_s_e_a_r_c_h_-_f_o_r_w_a_r_d and _i_-_s_e_a_r_c_h_- _b_a_c_k. hhiissttoorryy--sseeaarrcchh--ffoorrwwaarrdd (M-n, M-N) Like _h_i_s_t_o_r_y_-_s_e_a_r_c_h_-_b_a_c_k_w_a_r_d, but searches forward. ii--sseeaarrcchh--bbaacckk (not bound) Searches backward like _h_i_s_t_o_r_y_-_s_e_a_r_c_h_-_b_a_c_k_w_a_r_d, copies the first match into the input buffer with the cursor positioned at the end of the pattern, and prompts with `bck: ' and the first match. Additional characters may be typed to extend the search, _i_-_s_e_a_r_c_h_-_b_a_c_k may be typed to continue searching with the same pattern, wrapping around the history list if neces- sary, (_i_-_s_e_a_r_c_h_-_b_a_c_k must be bound to a single character for this to work) or one of the following special characters may be typed: ^W Appends the rest of the word under the cursor to the search pattern. delete (or any character bound to _b_a_c_k_w_a_r_d_-_d_e_l_e_t_e_-_c_h_a_r) Undoes the effect of the last character typed and deletes a character from the search pattern if appropriate. ^G If the previous search was successful, aborts the entire search. If not, goes back to the last suc- cessful search. escape Ends the search, leaving the current line in the input buffer. Any other character not bound to _s_e_l_f_-_i_n_s_e_r_t_-_c_o_m_m_a_n_d terminates the search, leaving the current line in the input buffer, and is then interpreted as normal input. In particular, a carriage return causes the current line to be executed. Emacs mode only. See also _i_-_s_e_a_r_c_h_-_f_w_d and _h_i_s_t_o_r_y_-_s_e_a_r_c_h_-_b_a_c_k_w_a_r_d. ii--sseeaarrcchh--ffwwdd (not bound) Like _i_-_s_e_a_r_c_h_-_b_a_c_k, but searches forward. iinnsseerrtt--llaasstt--wwoorrdd (M-_) Inserts the last word of the previous input line (`!$') into the input buffer. See also _c_o_p_y_-_p_r_e_v_-_w_o_r_d. lliisstt--cchhooiicceess (M-^D) Lists completion possibilities as described under CCoommpplleettiioonn aanndd lliissttiinngg. See also _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_l_i_s_t_-_o_r_-_e_o_f and _l_i_s_t_- _c_h_o_i_c_e_s_-_r_a_w. lliisstt--cchhooiicceess--rraaww (^X-^D) Like _l_i_s_t_-_c_h_o_i_c_e_s, but ignores user-defined completions. lliisstt--gglloobb (^X-g, ^X-G) Lists (via the _l_s_-_F builtin) matches to the glob-pattern (see FFiilleennaammee ssuubbssttiittuuttiioonn) to the left of the cursor. lliisstt--oorr--eeooff (not bound) Does _l_i_s_t_-_c_h_o_i_c_e_s or _e_n_d_-_o_f_-_f_i_l_e on an empty line. See also _d_e_l_e_t_e_-_c_h_a_r_-_o_r_-_l_i_s_t_-_o_r_-_e_o_f. mmaaggiicc--ssppaaccee (not bound) Expands history substitutions in the current line, like _e_x_p_a_n_d_- _h_i_s_t_o_r_y, and inserts a space. _m_a_g_i_c_-_s_p_a_c_e is designed to be bound to the space bar, but is not bound by default. nnoorrmmaalliizzee--ccoommmmaanndd (^X-?) Searches for the current word in PATH and, if it is found, replaces it with the full path to the executable. Special characters are quoted. Aliases are expanded and quoted but commands within aliases are not. This command is useful with commands that take commands as arguments, e.g., `dbx' and `sh -x'. nnoorrmmaalliizzee--ppaatthh (^X-n, ^X-N) Expands the current word as described under the `expand' set- ting of the ssyymmlliinnkkss shell variable. oovveerrwwrriittee--mmooddee (unbound) Toggles between input and overwrite modes. rruunn--ffgg--eeddiittoorr (M-^Z) Saves the current input line and looks for a stopped job with a name equal to the last component of the file name part of the EEDDIITTOORR or VVIISSUUAALL environment variables, or, if neither is set, `ed' or `vi'. If such a job is found, it is restarted as if `fg %_j_o_b' had been typed. This is used to toggle back and forth between an editor and the shell easily. Some people bind this command to `^Z' so they can do this even more easily. rruunn--hheellpp (M-h, M-H) Searches for documentation on the current command, using the same notion of `current command' as the completion routines, and prints it. There is no way to use a pager; _r_u_n_-_h_e_l_p is designed for short help files. If the special alias hheellppccoomm-- mmaanndd is defined, it is run with the command name as a sole argument. Else, documentation should be in a file named _c_o_m_- _m_a_n_d.help, _c_o_m_m_a_n_d.1, _c_o_m_m_a_n_d.6, _c_o_m_m_a_n_d.8 or _c_o_m_m_a_n_d, which should be in one of the directories listed in the HHPPAATTHH envi- ronment variable. If there is more than one help file only the first is printed. sseellff--iinnsseerrtt--ccoommmmaanndd (text characters) In insert mode (the default), inserts the typed character into the input line after the character under the cursor. In over- write mode, replaces the character under the cursor with the typed character. The input mode is normally preserved between lines, but the iinnppuuttmmooddee shell variable can be set to `insert' or `overwrite' to put the editor in that mode at the beginning of each line. See also _o_v_e_r_w_r_i_t_e_-_m_o_d_e. sseeqquueennccee--lleeaadd--iinn (arrow prefix, meta prefix, ^X) Indicates that the following characters are part of a multi-key sequence. Binding a command to a multi-key sequence really creates two bindings: the first character to _s_e_q_u_e_n_c_e_-_l_e_a_d_-_i_n and the whole sequence to the command. All sequences beginning with a character bound to _s_e_q_u_e_n_c_e_-_l_e_a_d_-_i_n are effectively bound to _u_n_d_e_f_i_n_e_d_-_k_e_y unless bound to another command. ssppeellll--lliinnee (M-$) Attempts to correct the spelling of each word in the input buffer, like _s_p_e_l_l_-_w_o_r_d, but ignores words whose first charac- ter is one of `-', `!', `^' or `%', or which contain `\', `*' or `?', to avoid problems with switches, substitutions and the like. See SSppeelllliinngg ccoorrrreeccttiioonn. ssppeellll--wwoorrdd (M-s, M-S) Attempts to correct the spelling of the current word as described under SSppeelllliinngg ccoorrrreeccttiioonn. Checks each component of a word which appears to be a pathname. ttooggggllee--lliitteerraall--hhiissttoorryy (M-r, M-R) Expands or `unexpands' history substitutions in the input buffer. See also _e_x_p_a_n_d_-_h_i_s_t_o_r_y and the aauuttooeexxppaanndd shell vari- able. uunnddeeffiinneedd--kkeeyy (any unbound key) Beeps. uupp--hhiissttoorryy (up-arrow, ^P) Copies the previous entry in the history list into the input buffer. If hhiissttlliitt is set, uses the literal form of the entry. May be repeated to step up through the history list, stopping at the top. vvii--sseeaarrcchh--bbaacckk (?) Prompts with `?' for a search string (which may be a glob-pat- tern, as with _h_i_s_t_o_r_y_-_s_e_a_r_c_h_-_b_a_c_k_w_a_r_d), searches for it and copies it into the input buffer. The bell rings if no match is found. Hitting return ends the search and leaves the last match in the input buffer. Hitting escape ends the search and executes the match. _v_i mode only. vvii--sseeaarrcchh--ffwwdd (/) Like _v_i_-_s_e_a_r_c_h_-_b_a_c_k, but searches forward. wwhhiicchh--ccoommmmaanndd (M-?) Does a _w_h_i_c_h (see the description of the builtin command) on the first word of the input buffer. yyaannkk--ppoopp (M-y) When executed immediately after a _y_a_n_k or another _y_a_n_k_-_p_o_p, replaces the yanked string with the next previous string from the killring. This also has the effect of rotating the kill- ring, such that this string will be considered the most recently killed by a later _y_a_n_k command. Repeating _y_a_n_k_-_p_o_p will cycle through the killring any number of times. LLeexxiiccaall ssttrruuccttuurree The shell splits input lines into words at blanks and tabs. The spe- cial characters `&', `|', `;', `<', `>', `(', and `)' and the doubled characters `&&', `||', `<<' and `>>' are always separate words, whether or not they are surrounded by whitespace. When the shell's input is not a terminal, the character `#' is taken to begin a comment. Each `#' and the rest of the input line on which it appears is discarded before further parsing. A special character (including a blank or tab) may be prevented from having its special meaning, and possibly made part of another word, by preceding it with a backslash (`\') or enclosing it in single (`''), double (`"') or backward (``') quotes. When not otherwise quoted a newline preceded by a `\' is equivalent to a blank, but inside quotes this sequence results in a newline. Furthermore, all SSuubbssttiittuuttiioonnss (see below) except HHiissttoorryy ssuubbssttiittuuttiioonn can be prevented by enclosing the strings (or parts of strings) in which they appear with single quotes or by quoting the crucial charac- ter(s) (e.g., `$' or ``' for VVaarriiaabbllee ssuubbssttiittuuttiioonn or CCoommmmaanndd ssuubbssttiittuu-- ttiioonn respectively) with `\'. (AAlliiaass ssuubbssttiittuuttiioonn is no exception: quoting in any way any character of a word for which an _a_l_i_a_s has been defined prevents substitution of the alias. The usual way of quoting an alias is to precede it with a backslash.) HHiissttoorryy ssuubbssttiittuuttiioonn is prevented by backslashes but not by single quotes. Strings quoted with double or backward quotes undergo VVaarriiaabbllee ssuubbssttiittuuttiioonn and CCoommmmaanndd ssuubbssttiittuuttiioonn, but other substitutions are prevented. Text inside single or double quotes becomes a single word (or part of one). Metacharacters in these strings, including blanks and tabs, do not form separate words. Only in one special case (see CCoommmmaanndd ssuubbssttii-- ttuuttiioonn below) can a double-quoted string yield parts of more than one word; single-quoted strings never do. Backward quotes are special: they signal CCoommmmaanndd ssuubbssttiittuuttiioonn (q.v.), which may result in more than one word. Quoting complex strings, particularly strings which themselves contain quoting characters, can be confusing. Remember that quotes need not be used as they are in human writing! It may be easier to quote not an entire string, but only those parts of the string which need quoting, using different types of quoting to do so if appropriate. The bbaacckkssllaasshh__qquuoottee shell variable (q.v.) can be set to make back- slashes always quote `\', `'', and `"'. (+) This may make complex quoting tasks easier, but it can cause syntax errors in _c_s_h(1) scripts. SSuubbssttiittuuttiioonnss We now describe the various transformations the shell performs on the input in the order in which they occur. We note in passing the data structures involved and the commands and variables which affect them. Remember that substitutions can be prevented by quoting as described under LLeexxiiccaall ssttrruuccttuurree. HHiissttoorryy ssuubbssttiittuuttiioonn Each command, or ``event'', input from the terminal is saved in the history list. The previous command is always saved, and the hhiissttoorryy shell variable can be set to a number to save that many commands. The hhiissttdduupp shell variable can be set to not save duplicate events or con- secutive duplicate events. Saved commands are numbered sequentially from 1 and stamped with the time. It is not usually necessary to use event numbers, but the cur- rent event number can be made part of the prompt by placing an `!' in the pprroommpptt shell variable. The shell actually saves history in expanded and literal (unexpanded) forms. If the hhiissttlliitt shell variable is set, commands that display and store history use the literal form. The _h_i_s_t_o_r_y builtin command can print, store in a file, restore and clear the history list at any time, and the ssaavveehhiisstt and hhiissttffiillee shell variables can be can be set to store the history list automatically on logout and restore it on login. History substitutions introduce words from the history list into the input stream, making it easy to repeat commands, repeat arguments of a previous command in the current command, or fix spelling mistakes in the previous command with little typing and a high degree of confi- dence. History substitutions begin with the character `!'. They may begin anywhere in the input stream, but they do not nest. The `!' may be preceded by a `\' to prevent its special meaning; for convenience, a `!' is passed unchanged when it is followed by a blank, tab, newline, `=' or `('. History substitutions also occur when an input line begins with `^'. This special abbreviation will be described later. The characters used to signal history substitution (`!' and `^') can be changed by setting the hhiissttcchhaarrss shell variable. Any input line which contains a history substitution is printed before it is executed. A history substitution may have an ``event specification'', which indi- cates the event from which words are to be taken, a ``word designa- tor'', which selects particular words from the chosen event, and/or a ``modifier'', which manipulates the selected words. An event specification can be _n A number, referring to a particular event -_n An offset, referring to the event _n before the current event # The current event. This should be used carefully in _c_s_h(1), where there is no check for recursion. _t_c_s_h allows 10 levels of recursion. (+) ! The previous event (equivalent to `-1') _s The most recent event whose first word begins with the string _s ?_s? The most recent event which contains the string _s. The second `?' can be omitted if it is immediately followed by a newline. For example, consider this bit of someone's history list: 9 8:30 nroff -man wumpus.man 10 8:31 cp wumpus.man wumpus.man.old 11 8:36 vi wumpus.man 12 8:37 diff wumpus.man.old wumpus.man The commands are shown with their event numbers and time stamps. The current event, which we haven't typed in yet, is event 13. `!11' and `!-2' refer to event 11. `!!' refers to the previous event, 12. `!!' can be abbreviated `!' if it is followed by `:' (`:' is described below). `!n' refers to event 9, which begins with `n'. `!?old?' also refers to event 12, which contains `old'. Without word designators or modifiers history references simply expand to the entire event, so we might type `!cp' to redo the copy command or `!!|more' if the `diff' output scrolled off the top of the screen. History references may be insulated from the surrounding text with braces if necessary. For example, `!vdoc' would look for a command beginning with `vdoc', and, in this example, not find one, but `!{v}doc' would expand unambiguously to `vi wumpus.mandoc'. Even in braces, history substitutions do not nest. (+) While _c_s_h(1) expands, for example, `!3d' to event 3 with the letter `d' appended to it, _t_c_s_h expands it to the last event beginning with `3d'; only completely numeric arguments are treated as event numbers. This makes it possible to recall events beginning with numbers. To expand `!3d' as in _c_s_h(1) say `!\3d'. To select words from an event we can follow the event specification by a `:' and a designator for the desired words. The words of an input line are numbered from 0, the first (usually command) word being 0, the second word (first argument) being 1, etc. The basic word designators are: 0 The first (command) word _n The _nth argument ^ The first argument, equivalent to `1' $ The last argument % The word matched by an ?_s? search _x_-_y A range of words _-_y Equivalent to _`_0_-_y_' * Equivalent to `^-$', but returns nothing if the event con- tains only 1 word _x_* Equivalent to _`_x_-_$_' _x_- Equivalent to _`_x_*_', but omitting the last word (`$') Selected words are inserted into the command line separated by single blanks. For example, the `diff' command in the previous example might have been typed as `diff !!:1.old !!:1' (using `:1' to select the first argument from the previous event) or `diff !-2:2 !-2:1' to select and swap the arguments from the `cp' command. If we didn't care about the order of the `diff' we might have said `diff !-2:1-2' or simply `diff !-2:*'. The `cp' command might have been written `cp wumpus.man !#:1.old', using `#' to refer to the current event. `!n:- hurkle.man' would reuse the first two words from the `nroff' command to say `nroff -man hurkle.man'. The `:' separating the event specification from the word designator can be omitted if the argument selector begins with a `^', `$', `*', `%' or `-'. For example, our `diff' command might have been `diff !!^.old !!^' or, equivalently, `diff !!$.old !!$'. However, if `!!' is abbre- viated `!', an argument selector beginning with `-' will be interpreted as an event specification. A history reference may have a word designator but no event specifica- tion. It then references the previous command. Continuing our `diff' example, we could have said simply `diff !^.old !^' or, to get the arguments in the opposite order, just `diff !*'. The word or words in a history reference can be edited, or ``modi- fied'', by following it with one or more modifiers, each preceded by a `:': h Remove a trailing pathname component, leaving the head. t Remove all leading pathname components, leaving the tail. r Remove a filename extension `.xxx', leaving the root name. e Remove all but the extension. u Uppercase the first lowercase letter. l Lowercase the first uppercase letter. s_/_l_/_r_/ Substitute _l for _r. _l is simply a string like _r, not a regular expression as in the eponymous _e_d(1) command. Any character may be used as the delimiter in place of `/'; a `\' can be used to quote the delimiter inside _l and _r. The character `&' in the _r is replaced by _l; `\' also quotes `&'. If _l is empty (``''), the _l from a previous substitu- tion or the _s from a previous `?_s?' event specification is used. The trailing delimiter may be omitted if it is imme- diately followed by a newline. & Repeat the previous substitution. g Apply the following modifier once to each word. a (+) Apply the following modifier as many times as possible to a single word. `a' and `g' can be used together to apply a modifier globally. In the current implementation, using the `a' and `s' modifiers together can lead to an infinite loop. For example, `:as/f/ff/' will never terminate. This behavior might change in the future. p Print the new command line but do not execute it. q Quote the substituted words, preventing further substitu- tions. x Like q, but break into words at blanks, tabs and newlines. Modifiers are applied to only the first modifiable word (unless `g' is used). It is an error for no word to be modifiable. For example, the `diff' command might have been written as `diff wum- pus.man.old !#^:r', using `:r' to remove `.old' from the first argument on the same line (`!#^'). We could say `echo hello out there', then `echo !*:u' to capitalize `hello', `echo !*:au' to say it out loud, or `echo !*:agu' to really shout. We might follow `mail -s "I forgot my password" rot' with `!:s/rot/root' to correct the spelling of `root' (but see SSppeelllliinngg ccoorrrreeccttiioonn for a different approach). There is a special abbreviation for substitutions. `^', when it is the first character on an input line, is equivalent to `!:s^'. Thus we might have said `^rot^root' to make the spelling correction in the pre- vious example. This is the only history substitution which does not explicitly begin with `!'. (+) In _c_s_h as such, only one modifier may be applied to each history or variable expansion. In _t_c_s_h, more than one may be used, for example % mv wumpus.man /usr/man/man1/wumpus.1 % man !$:t:r man wumpus In _c_s_h, the result would be `wumpus.1:r'. A substitution followed by a colon may need to be insulated from it with braces: > mv a.out /usr/games/wumpus > setenv PATH !$:h:$PATH Bad ! modifier: $. > setenv PATH !{-2$:h}:$PATH setenv PATH /usr/games:/bin:/usr/bin:. The first attempt would succeed in _c_s_h but fails in _t_c_s_h, because _t_c_s_h expects another modifier after the second colon rather than `$'. Finally, history can be accessed through the editor as well as through the substitutions just described. The _u_p_- and _d_o_w_n_-_h_i_s_t_o_r_y, _h_i_s_t_o_r_y_- _s_e_a_r_c_h_-_b_a_c_k_w_a_r_d and _-_f_o_r_w_a_r_d, _i_-_s_e_a_r_c_h_-_b_a_c_k and _-_f_w_d, _v_i_-_s_e_a_r_c_h_-_b_a_c_k and _-_f_w_d, _c_o_p_y_-_p_r_e_v_-_w_o_r_d and _i_n_s_e_r_t_-_l_a_s_t_-_w_o_r_d editor commands search for events in the history list and copy them into the input buffer. The _t_o_g_g_l_e_-_l_i_t_e_r_a_l_-_h_i_s_t_o_r_y editor command switches between the expanded and literal forms of history lines in the input buffer. _e_x_p_a_n_d_-_h_i_s_t_o_r_y and _e_x_p_a_n_d_-_l_i_n_e expand history substitutions in the current word and in the entire input buffer respectively. AAlliiaass ssuubbssttiittuuttiioonn The shell maintains a list of aliases which can be set, unset and printed by the _a_l_i_a_s and _u_n_a_l_i_a_s commands. After a command line is parsed into simple commands (see CCoommmmaannddss) the first word of each com- mand, left-to-right, is checked to see if it has an alias. If so, the first word is replaced by the alias. If the alias contains a history reference, it undergoes HHiissttoorryy ssuubbssttiittuuttiioonn (q.v.) as though the orig- inal command were the previous input line. If the alias does not con- tain a history reference, the argument list is left untouched. Thus if the alias for `ls' were `ls -l' the command `ls /usr' would become `ls -l /usr', the argument list here being undisturbed. If the alias for `lookup' were `grep !^ /etc/passwd' then `lookup bill' would become `grep bill /etc/passwd'. Aliases can be used to introduce parser metasyntax. For example, `alias print 'pr \!* | lpr'' defines a ``command'' (`print') which _p_r(1)s its arguments to the line printer. Alias substitution is repeated until the first word of the command has no alias. If an alias substitution does not change the first word (as in the previous example) it is flagged to prevent a loop. Other loops are detected and cause an error. Some aliases are referred to by the shell; see SSppeecciiaall aalliiaasseess. VVaarriiaabbllee ssuubbssttiittuuttiioonn The shell maintains a list of variables, each of which has as value a list of zero or more words. The values of shell variables can be dis- played and changed with the _s_e_t and _u_n_s_e_t commands. The system main- tains its own list of ``environment'' variables. These can be dis- played and changed with _p_r_i_n_t_e_n_v, _s_e_t_e_n_v and _u_n_s_e_t_e_n_v. (+) Variables may be made read-only with `set -r' (q.v.) Read-only variables may not be modified or unset; attempting to do so will cause an error. Once made read-only, a variable cannot be made writable, so `set -r' should be used with caution. Environment variables cannot be made read-only. Some variables are set by the shell or referred to by it. For instance, the aarrggvv variable is an image of the shell's argument list, and words of this variable's value are referred to in special ways. Some of the variables referred to by the shell are toggles; the shell does not care what their value is, only whether they are set or not. For instance, the vveerrbboossee variable is a toggle which causes command input to be echoed. The --vv command line option sets this variable. SSppeecciiaall sshheellll vvaarriiaabblleess lists all variables which are referred to by the shell. Other operations treat variables numerically. The `@' command permits numeric calculations to be performed and the result assigned to a vari- able. Variable values are, however, always represented as (zero or more) strings. For the purposes of numeric operations, the null string is considered to be zero, and the second and subsequent words of multi- word values are ignored. After the input line is aliased and parsed, and before each command is executed, variable substitution is performed keyed by `$' characters. This expansion can be prevented by preceding the `$' with a `\' except within `"'s where it _a_l_w_a_y_s occurs, and within `''s where it _n_e_v_e_r occurs. Strings quoted by ``' are interpreted later (see CCoommmmaanndd ssuubb-- ssttiittuuttiioonn below) so `$' substitution does not occur there until later, if at all. A `$' is passed unchanged if followed by a blank, tab, or end-of-line. Input/output redirections are recognized before variable expansion, and are variable expanded separately. Otherwise, the command name and entire argument list are expanded together. It is thus possible for the first (command) word (to this point) to generate more than one word, the first of which becomes the command name, and the rest of which become arguments. Unless enclosed in `"' or given the `:q' modifier the results of vari- able substitution may eventually be command and filename substituted. Within `"', a variable whose value consists of multiple words expands to a (portion of a) single word, with the words of the variable's value separated by blanks. When the `:q' modifier is applied to a substitu- tion the variable will expand to multiple words with each word sepa- rated by a blank and quoted to prevent later command or filename sub- stitution. The following metasequences are provided for introducing variable val- ues into the shell input. Except as noted, it is an error to reference a variable which is not set. $_n_a_m_e ${_n_a_m_e} Substitutes the words of the value of variable _n_a_m_e, each sepa- rated by a blank. Braces insulate _n_a_m_e from following charac- ters which would otherwise be part of it. Shell variables have names consisting of up to 20 letters and digits starting with a letter. The underscore character is considered a letter. If _n_a_m_e is not a shell variable, but is set in the environment, then that value is returned (but `:' modifiers and the other forms given below are not available in this case). $_n_a_m_e[_s_e_l_e_c_t_o_r] ${_n_a_m_e[_s_e_l_e_c_t_o_r]} Substitutes only the selected words from the value of _n_a_m_e. The _s_e_l_e_c_t_o_r is subjected to `$' substitution and may consist of a single number or two numbers separated by a `-'. The first word of a variable's value is numbered `1'. If the first number of a range is omitted it defaults to `1'. If the last member of a range is omitted it defaults to `$#_n_a_m_e'. The _s_e_l_e_c_t_o_r `*' selects all words. It is not an error for a range to be empty if the second argument is omitted or in range. $0 Substitutes the name of the file from which command input is being read. An error occurs if the name is not known. $_n_u_m_b_e_r ${_n_u_m_b_e_r} Equivalent to `$argv[_n_u_m_b_e_r]'. $* Equivalent to `$argv', which is equivalent to `$argv[*]'. The `:' modifiers described under HHiissttoorryy ssuubbssttiittuuttiioonn, except for `:p', can be applied to the substitutions above. More than one may be used. (+) Braces may be needed to insulate a variable substitution from a literal colon just as with HHiissttoorryy ssuubbssttiittuuttiioonn (q.v.); any mod- ifiers must appear within the braces. The following substitutions can not be modified with `:' modifiers. $?_n_a_m_e ${?_n_a_m_e} Substitutes the string `1' if _n_a_m_e is set, `0' if it is not. $?0 Substitutes `1' if the current input filename is known, `0' if it is not. Always `0' in interactive shells. $#_n_a_m_e ${#_n_a_m_e} Substitutes the number of words in _n_a_m_e. $# Equivalent to `$#argv'. (+) $%_n_a_m_e ${%_n_a_m_e} Substitutes the number of characters in _n_a_m_e. (+) $%_n_u_m_b_e_r ${%_n_u_m_b_e_r} Substitutes the number of characters in $argv[_n_u_m_b_e_r]. (+) $? Equivalent to `$status'. (+) $$ Substitutes the (decimal) process number of the (parent) shell. $! Substitutes the (decimal) process number of the last background process started by this shell. (+) $_ Substitutes the command line of the last command executed. (+) $< Substitutes a line from the standard input, with no further interpretation thereafter. It can be used to read from the keyboard in a shell script. (+) While _c_s_h always quotes $<, as if it were equivalent to `$<:q', _t_c_s_h does not. Furthermore, when _t_c_s_h is waiting for a line to be typed the user may type an interrupt to interrupt the sequence into which the line is to be substituted, but _c_s_h does not allow this. The editor command _e_x_p_a_n_d_-_v_a_r_i_a_b_l_e_s, normally bound to `^X-$', can be used to interactively expand individual variables. CCoommmmaanndd,, ffiilleennaammee aanndd ddiirreeccttoorryy ssttaacckk ssuubbssttiittuuttiioonn The remaining substitutions are applied selectively to the arguments of builtin commands. This means that portions of expressions which are not evaluated are not subjected to these expansions. For commands which are not internal to the shell, the command name is substituted separately from the argument list. This occurs very late, after input- output redirection is performed, and in a child of the main shell. CCoommmmaanndd ssuubbssttiittuuttiioonn Command substitution is indicated by a command enclosed in ``'. The output from such a command is broken into separate words at blanks, tabs and newlines, and null words are discarded. The output is vari- able and command substituted and put in place of the original string. Command substitutions inside double quotes (`"') retain blanks and tabs; only newlines force new words. The single final newline does not force a new word in any case. It is thus possible for a command sub- stitution to yield only part of a word, even if the command outputs a complete line. By default, the shell since version 6.12 replaces all newline and car- riage return characters in the command by spaces. If this is switched off by unsetting ccssuubbssttnnoonnll, newlines separate commands as usual. FFiilleennaammee ssuubbssttiittuuttiioonn If a word contains any of the characters `*', `?', `[' or `{' or begins with the character `~' it is a candidate for filename substitution, also known as ``globbing''. This word is then regarded as a pattern (``glob-pattern''), and replaced with an alphabetically sorted list of file names which match the pattern. In matching filenames, the character `.' at the beginning of a filename or immediately following a `/', as well as the character `/' must be matched explicitly. The character `*' matches any string of charac- ters, including the null string. The character `?' matches any single character. The sequence `[...]' matches any one of the characters enclosed. Within `[...]', a pair of characters separated by `-' matches any character lexically between the two. (+) Some glob-patterns can be negated: The sequence `[^...]' matches any single character _n_o_t specified by the characters and/or ranges of characters in the braces. An entire glob-pattern can also be negated with `^': > echo * bang crash crunch ouch > echo ^cr* bang ouch Glob-patterns which do not use `?', `*', or `[]' or which use `{}' or `~' (below) are not negated correctly. The metanotation `a{b,c,d}e' is a shorthand for `abe ace ade'. Left- to-right order is preserved: `/usr/source/s1/{oldls,ls}.c' expands to `/usr/source/s1/oldls.c /usr/source/s1/ls.c'. The results of matches are sorted separately at a low level to preserve this order: `../{memo,*box}' might expand to `../memo ../box ../mbox'. (Note that `memo' was not sorted with the results of matching `*box'.) It is not an error when this construct expands to files which do not exist, but it is possible to get an error from a command to which the expanded list is passed. This construct may be nested. As a special case the words `{', `}' and `{}' are passed undisturbed. The character `~' at the beginning of a filename refers to home direc- tories. Standing alone, i.e., `~', it expands to the invoker's home directory as reflected in the value of the hhoommee shell variable. When followed by a name consisting of letters, digits and `-' characters the shell searches for a user with that name and substitutes their home directory; thus `~ken' might expand to `/usr/ken' and `~ken/chmach' to `/usr/ken/chmach'. If the character `~' is followed by a character other than a letter or `/' or appears elsewhere than at the beginning of a word, it is left undisturbed. A command like `setenv MANPATH /usr/man:/usr/local/man:~/lib/man' does not, therefore, do home direc- tory substitution as one might hope. It is an error for a glob-pattern containing `*', `?', `[' or `~', with or without `^', not to match any files. However, only one pattern in a list of glob-patterns must match a file (so that, e.g., `rm *.a *.c *.o' would fail only if there were no files in the current directory ending in `.a', `.c', or `.o'), and if the nnoonnoommaattcchh shell variable is set a pattern (or list of patterns) which matches nothing is left unchanged rather than causing an error. The nnoogglloobb shell variable can be set to prevent filename substitution, and the _e_x_p_a_n_d_-_g_l_o_b editor command, normally bound to `^X-*', can be used to interactively expand individual filename substitutions. DDiirreeccttoorryy ssttaacckk ssuubbssttiittuuttiioonn ((++)) The directory stack is a list of directories, numbered from zero, used by the _p_u_s_h_d, _p_o_p_d and _d_i_r_s builtin commands (q.v.). _d_i_r_s can print, store in a file, restore and clear the directory stack at any time, and the ssaavveeddiirrss and ddiirrssffiillee shell variables can be set to store the directory stack automatically on logout and restore it on login. The ddiirrssttaacckk shell variable can be examined to see the directory stack and set to put arbitrary directories into the directory stack. The character `=' followed by one or more digits expands to an entry in the directory stack. The special case `=-' expands to the last direc- tory in the stack. For example, > dirs -v 0 /usr/bin 1 /usr/spool/uucp 2 /usr/accts/sys > echo =1 /usr/spool/uucp > echo =0/calendar /usr/bin/calendar > echo =- /usr/accts/sys The nnoogglloobb and nnoonnoommaattcchh shell variables and the _e_x_p_a_n_d_-_g_l_o_b editor command apply to directory stack as well as filename substitutions. OOtthheerr ssuubbssttiittuuttiioonnss ((++)) There are several more transformations involving filenames, not strictly related to the above but mentioned here for completeness. _A_n_y filename may be expanded to a full path when the ssyymmlliinnkkss variable (q.v.) is set to `expand'. Quoting prevents this expansion, and the _n_o_r_m_a_l_i_z_e_-_p_a_t_h editor command does it on demand. The _n_o_r_m_a_l_i_z_e_-_c_o_m_m_a_n_d editor command expands commands in PATH into full paths on demand. Finally, _c_d and _p_u_s_h_d interpret `-' as the old working directory (equivalent to the shell variable oowwdd). This is not a substitution at all, but an abbreviation recognized by only those commands. Nonethe- less, it too can be prevented by quoting. CCoommmmaannddss The next three sections describe how the shell executes commands and deals with their input and output. SSiimmppllee ccoommmmaannddss,, ppiippeelliinneess aanndd sseeqquueenncceess A simple command is a sequence of words, the first of which specifies the command to be executed. A series of simple commands joined by `|' characters forms a pipeline. The output of each command in a pipeline is connected to the input of the next. Simple commands and pipelines may be joined into sequences with `;', and will be executed sequentially. Commands and pipelines can also be joined into sequences with `||' or `&&', indicating, as in the C lan- guage, that the second is to be executed only if the first fails or succeeds respectively. A simple command, pipeline or sequence may be placed in parentheses, `()', to form a simple command, which may in turn be a component of a pipeline or sequence. A command, pipeline or sequence can be executed without waiting for it to terminate by following it with an `&'. BBuuiillttiinn aanndd nnoonn--bbuuiillttiinn ccoommmmaanndd eexxeeccuuttiioonn Builtin commands are executed within the shell. If any component of a pipeline except the last is a builtin command, the pipeline is executed in a subshell. Parenthesized commands are always executed in a subshell. (cd; pwd); pwd thus prints the hhoommee directory, leaving you where you were (printing this after the home directory), while cd; pwd leaves you in the hhoommee directory. Parenthesized commands are most often used to prevent _c_d from affecting the current shell. When a command to be executed is found not to be a builtin command the shell attempts to execute the command via _e_x_e_c_v_e(2). Each word in the variable ppaatthh names a directory in which the shell will look for the command. If it is given neither a --cc nor a --tt option, the shell hashes the names in these directories into an internal table so that it will try an _e_x_e_c_v_e(2) in only a directory where there is a possibility that the command resides there. This greatly speeds command location when a large number of directories are present in the search path. If this mechanism has been turned off (via _u_n_h_a_s_h), if the shell was given a --cc or --tt argument or in any case for each directory component of ppaatthh which does not begin with a `/', the shell concatenates the current working directory with the given command name to form a path name of a file which it then attempts to execute. If the file has execute permissions but is not an executable to the system (i.e., it is neither an executable binary nor a script that specifies its interpreter), then it is assumed to be a file containing shell commands and a new shell is spawned to read it. The _s_h_e_l_l spe- cial alias may be set to specify an interpreter other than the shell itself. On systems which do not understand the `#!' script interpreter conven- tion the shell may be compiled to emulate it; see the vveerrssiioonn shell variable. If so, the shell checks the first line of the file to see if it is of the form `#!_i_n_t_e_r_p_r_e_t_e_r _a_r_g ...'. If it is, the shell starts _i_n_t_e_r_p_r_e_t_e_r with the given _a_r_gs and feeds the file to it on standard input. IInnppuutt//oouuttppuutt The standard input and standard output of a command may be redirected with the following syntax: < _n_a_m_e Open file _n_a_m_e (which is first variable, command and filename expanded) as the standard input. << _w_o_r_d Read the shell input up to a line which is identical to _w_o_r_d. _w_o_r_d is not subjected to variable, filename or command substi- tution, and each input line is compared to _w_o_r_d before any sub- stitutions are done on this input line. Unless a quoting `\', `"', `' or ``' appears in _w_o_r_d variable and command substitu- tion is performed on the intervening lines, allowing `\' to quote `$', `\' and ``'. Commands which are substituted have all blanks, tabs, and newlines preserved, except for the final newline which is dropped. The resultant text is placed in an anonymous temporary file which is given to the command as stan- dard input. > _n_a_m_e _>_! _n_a_m_e _>_& _n_a_m_e _>_&_! _n_a_m_e The file _n_a_m_e is used as standard output. If the file does not exist then it is created; if the file exists, it is truncated, its previous contents being lost. If the shell variable nnoocclloobbbbeerr is set, then the file must not exist or be a character special file (e.g., a terminal or `/dev/null') or an error results. This helps prevent acciden- tal destruction of files. In this case the `!' forms can be used to suppress this check. The forms involving `&' route the diagnostic output into the specified file as well as the standard output. _n_a_m_e is expanded in the same way as `<' input filenames are. >> _n_a_m_e _>_>_& _n_a_m_e _>_>_! _n_a_m_e _>_>_&_! _n_a_m_e Like `>', but appends output to the end of _n_a_m_e. If the shell variable nnoocclloobbbbeerr is set, then it is an error for the file _n_o_t to exist, unless one of the `!' forms is given. A command receives the environment in which the shell was invoked as modified by the input-output parameters and the presence of the command in a pipeline. Thus, unlike some previous shells, commands run from a file of shell commands have no access to the text of the commands by default; rather they receive the original standard input of the shell. The `<<' mechanism should be used to present inline data. This permits shell command scripts to function as components of pipelines and allows the shell to block read its input. Note that the default standard input for a command run detached is _n_o_t the empty file _/_d_e_v_/_n_u_l_l, but the original standard input of the shell. If this is a terminal and if the process attempts to read from the terminal, then the process will block and the user will be notified (see JJoobbss). Diagnostic output may be directed through a pipe with the standard out- put. Simply use the form `|&' rather than just `|'. The shell cannot presently redirect diagnostic output without also redirecting standard output, but `(_c_o_m_m_a_n_d > _o_u_t_p_u_t_-_f_i_l_e) >& _e_r_r_o_r_- _f_i_l_e' is often an acceptable workaround. Either _o_u_t_p_u_t_-_f_i_l_e or _e_r_r_o_r_- _f_i_l_e may be `/dev/tty' to send output to the terminal. FFeeaattuurreess Having described how the shell accepts, parses and executes command lines, we now turn to a variety of its useful features. CCoonnttrrooll ffllooww The shell contains a number of commands which can be used to regulate the flow of control in command files (shell scripts) and (in limited but useful ways) from terminal input. These commands all operate by forcing the shell to reread or skip in its input and, due to the imple- mentation, restrict the placement of some of the commands. The _f_o_r_e_a_c_h, _s_w_i_t_c_h, and _w_h_i_l_e statements, as well as the _i_f_-_t_h_e_n_-_e_l_s_e form of the _i_f statement, require that the major keywords appear in a single simple command on an input line as shown below. If the shell's input is not seekable, the shell buffers up input when- ever a loop is being read and performs seeks in this internal buffer to accomplish the rereading implied by the loop. (To the extent that this allows, backward _g_o_t_os will succeed on non-seekable inputs.) EExxpprreessssiioonnss The _i_f, _w_h_i_l_e and _e_x_i_t builtin commands use expressions with a common syntax. The expressions can include any of the operators described in the next three sections. Note that the _@ builtin command (q.v.) has its own separate syntax. LLooggiiccaall,, aarriitthhmmeettiiccaall aanndd ccoommppaarriissoonn ooppeerraattoorrss These operators are similar to those of C and have the same precedence. They include || && | ^ & == != =~ !~ <= >= < > << >> + - * / % ! ~ ( ) Here the precedence increases to the right, `==' `!=' `=~' and `!~', `<=' `>=' `<' and `>', `<<' and `>>', `+' and `-', `*' `/' and `%' being, in groups, at the same level. The `==' `!=' `=~' and `!~' oper- ators compare their arguments as strings; all others operate on num- bers. The operators `=~' and `!~' are like `!=' and `==' except that the right hand side is a glob-pattern (see FFiilleennaammee ssuubbssttiittuuttiioonn) against which the left hand operand is matched. This reduces the need for use of the _s_w_i_t_c_h builtin command in shell scripts when all that is really needed is pattern matching. Strings which begin with `0' are considered octal numbers. Null or missing arguments are considered `0'. The results of all expressions are strings, which represent decimal numbers. It is important to note that no two components of an expression can appear in the same word; except when adjacent to components of expressions which are syntacti- cally significant to the parser (`&' `|' `<' `>' `(' `)') they should be surrounded by spaces. CCoommmmaanndd eexxiitt ssttaattuuss Commands can be executed in expressions and their exit status returned by enclosing them in braces (`{}'). Remember that the braces should be separated from the words of the command by spaces. Command executions succeed, returning true, i.e., `1', if the command exits with status 0, otherwise they fail, returning false, i.e., `0'. If more detailed sta- tus information is required then the command should be executed outside of an expression and the ssttaattuuss shell variable examined. FFiillee iinnqquuiirryy ooppeerraattoorrss Some of these operators perform true/false tests on files and related objects. They are of the form --_o_p _f_i_l_e, where _o_p is one of rr Read access ww Write access xx Execute access XX Executable in the path or shell builtin, e.g., `-X ls' and `-X ls-F' are generally true, but `-X /bin/ls' is not (+) ee Existence oo Ownership zz Zero size ss Non-zero size (+) ff Plain file dd Directory ll Symbolic link (+) * bb Block special file (+) cc Character special file (+) pp Named pipe (fifo) (+) * SS Socket special file (+) * uu Set-user-ID bit is set (+) gg Set-group-ID bit is set (+) kk Sticky bit is set (+) tt _f_i_l_e (which must be a digit) is an open file descriptor for a terminal device (+) RR Has been migrated (convex only) (+) LL Applies subsequent operators in a multiple-operator test to a symbolic link rather than to the file to which the link points (+) * _f_i_l_e is command and filename expanded and then tested to see if it has the specified relationship to the real user. If _f_i_l_e does not exist or is inaccessible or, for the operators indicated by `*', if the speci- fied file type does not exist on the current system, then all enquiries return false, i.e., `0'. These operators may be combined for conciseness: `-_x_y _f_i_l_e' is equiva- lent to `-_x _f_i_l_e && -_y _f_i_l_e'. (+) For example, `-fx' is true (returns `1') for plain executable files, but not for directories. LL may be used in a multiple-operator test to apply subsequent operators to a symbolic link rather than to the file to which the link points. For example, `-lLo' is true for links owned by the invoking user. LLrr, LLww and LLxx are always true for links and false for non-links. LL has a different meaning when it is the last operator in a multiple-operator test; see below. It is possible but not useful, and sometimes misleading, to combine operators which expect _f_i_l_e to be a file with operators which do not, (e.g., XX and tt). Following LL with a non-file operator can lead to par- ticularly strange results. Other operators return other information, i.e., not just `0' or `1'. (+) They have the same format as before; _o_p may be one of AA Last file access time, as the number of seconds since the epoch AA:: Like AA, but in timestamp format, e.g., `Fri May 14 16:36:10 1993' MM Last file modification time MM:: Like MM, but in timestamp format CC Last inode modification time CC:: Like CC, but in timestamp format DD Device number II Inode number FF Composite ffile identifier, in the form _d_e_v_i_c_e:_i_n_o_d_e LL The name of the file pointed to by a symbolic link NN Number of (hard) links PP Permissions, in octal, without leading zero PP:: Like PP, with leading zero PP_m_o_d_e Equivalent to `-P _f_i_l_e & _m_o_d_e', e.g., `-P22 _f_i_l_e' returns `22' if _f_i_l_e is writable by group and other, `20' if by group only, and `0' if by neither PP_m_o_d_e:: Like PP_m_o_d_e::, with leading zero UU Numeric userid UU:: Username, or the numeric userid if the username is unknown GG Numeric groupid GG:: Groupname, or the numeric groupid if the groupname is unknown ZZ Size, in bytes Only one of these operators may appear in a multiple-operator test, and it must be the last. Note that LL has a different meaning at the end of and elsewhere in a multiple-operator test. Because `0' is a valid return value for many of these operators, they do not return `0' when they fail: most return `-1', and FF returns `:'. If the shell is compiled with POSIX defined (see the vveerrssiioonn shell variable), the result of a file inquiry is based on the permission bits of the file and not on the result of the _a_c_c_e_s_s(2) system call. For example, if one tests a file with --ww whose permissions would ordinarily allow writing but which is on a file system mounted read-only, the test will succeed in a POSIX shell but fail in a non-POSIX shell. File inquiry operators can also be evaluated with the _f_i_l_e_t_e_s_t builtin command (q.v.) (+). JJoobbss The shell associates a _j_o_b with each pipeline. It keeps a table of current jobs, printed by the _j_o_b_s command, and assigns them small inte- ger numbers. When a job is started asynchronously with `&', the shell prints a line which looks like [1] 1234 indicating that the job which was started asynchronously was job number 1 and had one (top-level) process, whose process id was 1234. If you are running a job and wish to do something else you may hit the suspend key (usually `^Z'), which sends a STOP signal to the current job. The shell will then normally indicate that the job has been `Sus- pended' and print another prompt. If the lliissttjjoobbss shell variable is set, all jobs will be listed like the _j_o_b_s builtin command; if it is set to `long' the listing will be in long format, like `jobs -l'. You can then manipulate the state of the suspended job. You can put it in the ``background'' with the _b_g command or run some other commands and eventually bring the job back into the ``foreground'' with _f_g. (See also the _r_u_n_-_f_g_-_e_d_i_t_o_r editor command.) A `^Z' takes effect immedi- ately and is like an interrupt in that pending output and unread input are discarded when it is typed. The _w_a_i_t builtin command causes the shell to wait for all background jobs to complete. The `^]' key sends a delayed suspend signal, which does not generate a STOP signal until a program attempts to _r_e_a_d(2) it, to the current job. This can usefully be typed ahead when you have prepared some commands for a job which you wish to stop after it has read them. The `^Y' key performs this function in _c_s_h(1); in _t_c_s_h, `^Y' is an editing command. (+) A job being run in the background stops if it tries to read from the terminal. Background jobs are normally allowed to produce output, but this can be disabled by giving the command `stty tostop'. If you set this tty option, then background jobs will stop when they try to pro- duce output like they do when they try to read input. There are several ways to refer to jobs in the shell. The character `%' introduces a job name. If you wish to refer to job number 1, you can name it as `%1'. Just naming a job brings it to the foreground; thus `%1' is a synonym for `fg %1', bringing job 1 back into the fore- ground. Similarly, saying `%1 &' resumes job 1 in the background, just like `bg %1'. A job can also be named by an unambiguous prefix of the string typed in to start it: `%ex' would normally restart a suspended _e_x(1) job, if there were only one suspended job whose name began with the string `ex'. It is also possible to say `%?_s_t_r_i_n_g' to specify a job whose text contains _s_t_r_i_n_g, if there is only one such job. The shell maintains a notion of the current and previous jobs. In out- put pertaining to jobs, the current job is marked with a `+' and the previous job with a `-'. The abbreviations `%+', `%', and (by analogy with the syntax of the _h_i_s_t_o_r_y mechanism) `%%' all refer to the current job, and `%-' refers to the previous job. The job control mechanism requires that the _s_t_t_y(1) option `new' be set on some systems. It is an artifact from a `new' implementation of the tty driver which allows generation of interrupt characters from the keyboard to tell jobs to stop. See _s_t_t_y(1) and the _s_e_t_t_y builtin com- mand for details on setting options in the new tty driver. SSttaattuuss rreeppoorrttiinngg The shell learns immediately whenever a process changes state. It nor- mally informs you whenever a job becomes blocked so that no further progress is possible, but only right before it prints a prompt. This is done so that it does not otherwise disturb your work. If, however, you set the shell variable nnoottiiffyy, the shell will notify you immedi- ately of changes of status in background jobs. There is also a shell command _n_o_t_i_f_y which marks a single process so that its status changes will be immediately reported. By default _n_o_t_i_f_y marks the current process; simply say `notify' after starting a background job to mark it. When you try to leave the shell while jobs are stopped, you will be warned that `You have stopped jobs.' You may use the _j_o_b_s command to see what they are. If you do this or immediately try to exit again, the shell will not warn you a second time, and the suspended jobs will be terminated. AAuuttoommaattiicc,, ppeerriiooddiicc aanndd ttiimmeedd eevveennttss ((++)) There are various ways to run commands and take other actions automati- cally at various times in the ``life cycle'' of the shell. They are summarized here, and described in detail under the appropriate BBuuiillttiinn ccoommmmaannddss, SSppeecciiaall sshheellll vvaarriiaabblleess and SSppeecciiaall aalliiaasseess. The _s_c_h_e_d builtin command puts commands in a scheduled-event list, to be executed by the shell at a given time. The _b_e_e_p_c_m_d, _c_w_d_c_m_d, _p_e_r_i_o_d_i_c, _p_r_e_c_m_d, _p_o_s_t_c_m_d, and _j_o_b_c_m_d SSppeecciiaall aalliiaasseess can be set, respectively, to execute commands when the shell wants to ring the bell, when the working directory changes, every ttppee-- rriioodd minutes, before each prompt, before each command gets executed, after each command gets executed, and when a job is started or is brought into the foreground. The aauuttoollooggoouutt shell variable can be set to log out or lock the shell after a given number of minutes of inactivity. The mmaaiill shell variable can be set to check for new mail periodically. The pprriinntteexxiittvvaalluuee shell variable can be set to print the exit status of commands which exit with a status other than zero. The rrmmssttaarr shell variable can be set to ask the user, when `rm *' is typed, if that is really what was meant. The ttiimmee shell variable can be set to execute the _t_i_m_e builtin command after the completion of any process that takes more than a given number of CPU seconds. The wwaattcchh and wwhhoo shell variables can be set to report when selected users log in or out, and the _l_o_g builtin command reports on those users at any time. NNaattiivvee LLaanngguuaaggee SSyysstteemm ssuuppppoorrtt ((++)) The shell is eight bit clean (if so compiled; see the vveerrssiioonn shell variable) and thus supports character sets needing this capability. NLS support differs depending on whether or not the shell was compiled to use the system's NLS (again, see vveerrssiioonn). In either case, 7-bit ASCII is the default character code (e.g., the classification of which characters are printable) and sorting, and changing the LLAANNGG or LLCC__CCTTYYPPEE environment variables causes a check for possible changes in these respects. When using the system's NLS, the _s_e_t_l_o_c_a_l_e(3) function is called to determine appropriate character code/classification and sorting (e.g., a 'en_CA.UTF-8' would yield "UTF-8" as a character code). This func- tion typically examines the LLAANNGG and LLCC__CCTTYYPPEE environment variables; refer to the system documentation for further details. When not using the system's NLS, the shell simulates it by assuming that the ISO 8859-1 character set is used whenever either of the LLAANNGG and LLCC__CCTTYYPPEE variables are set, regardless of their values. Sorting is not affected for the simulated NLS. In addition, with both real and simulated NLS, all printable characters in the range \200-\377, i.e., those that have M-_c_h_a_r bindings, are automatically rebound to _s_e_l_f_-_i_n_s_e_r_t_-_c_o_m_m_a_n_d. The corresponding bind- ing for the escape-_c_h_a_r sequence, if any, is left alone. These charac- ters are not rebound if the NNOORREEBBIINNDD environment variable is set. This may be useful for the simulated NLS or a primitive real NLS which assumes full ISO 8859-1. Otherwise, all M-_c_h_a_r bindings in the range \240-\377 are effectively undone. Explicitly rebinding the relevant keys with _b_i_n_d_k_e_y is of course still possible. Unknown characters (i.e., those that are neither printable nor control characters) are printed in the format \nnn. If the tty is not in 8 bit mode, other 8 bit characters are printed by converting them to ASCII and using standout mode. The shell never changes the 7/8 bit mode of the tty and tracks user-initiated changes of 7/8 bit mode. NLS users (or, for that matter, those who want to use a meta key) may need to explicitly set the tty in 8 bit mode through the appropriate _s_t_t_y(1) command in, e.g., the _~_/_._l_o_g_i_n file. OOSS vvaarriiaanntt ssuuppppoorrtt ((++)) A number of new builtin commands are provided to support features in particular operating systems. All are described in detail in the BBuuiillttiinn ccoommmmaannddss section. On systems that support TCF (aix-ibm370, aix-ps2), _g_e_t_s_p_a_t_h and _s_e_t_s_p_a_t_h get and set the system execution path, _g_e_t_x_v_e_r_s and _s_e_t_x_v_e_r_s get and set the experimental version prefix and _m_i_g_r_a_t_e migrates pro- cesses between sites. The _j_o_b_s builtin prints the site on which each job is executing. Under BS2000, _b_s_2_c_m_d executes commands of the underlying BS2000/OSD operating system. Under Domain/OS, _i_n_l_i_b adds shared libraries to the current environ- ment, _r_o_o_t_n_o_d_e changes the rootnode and _v_e_r changes the systype. Under Mach, _s_e_t_p_a_t_h is equivalent to Mach's _s_e_t_p_a_t_h(1). Under Masscomp/RTU and Harris CX/UX, _u_n_i_v_e_r_s_e sets the universe. Under Harris CX/UX, _u_c_b or _a_t_t runs a command under the specified uni- verse. Under Convex/OS, _w_a_r_p prints or sets the universe. The VVEENNDDOORR, OOSSTTYYPPEE and MMAACCHHTTYYPPEE environment variables indicate respec- tively the vendor, operating system and machine type (microprocessor class or machine model) of the system on which the shell thinks it is running. These are particularly useful when sharing one's home direc- tory between several types of machines; one can, for example, set path = (~/bin.$MACHTYPE /usr/ucb /bin /usr/bin .) in one's _~_/_._l_o_g_i_n and put executables compiled for each machine in the appropriate directory. The vveerrssiioonn shell variable indicates what options were chosen when the shell was compiled. Note also the _n_e_w_g_r_p builtin, the aaffssuusseerr and eecchhoo__ssttyyllee shell vari- ables and the system-dependent locations of the shell's input files (see FFIILLEESS). SSiiggnnaall hhaannddlliinngg Login shells ignore interrupts when reading the file _~_/_._l_o_g_o_u_t. The shell ignores quit signals unless started with --qq. Login shells catch the terminate signal, but non-login shells inherit the terminate behav- ior from their parents. Other signals have the values which the shell inherited from its parent. In shell scripts, the shell's handling of interrupt and terminate sig- nals can be controlled with _o_n_i_n_t_r, and its handling of hangups can be controlled with _h_u_p and _n_o_h_u_p. The shell exits on a hangup (see also the llooggoouutt shell variable). By default, the shell's children do too, but the shell does not send them a hangup when it exits. _h_u_p arranges for the shell to send a hangup to a child when it exits, and _n_o_h_u_p sets a child to ignore hangups. TTeerrmmiinnaall mmaannaaggeemmeenntt ((++)) The shell uses three different sets of terminal (``tty'') modes: `edit', used when editing, `quote', used when quoting literal charac- ters, and `execute', used when executing commands. The shell holds some settings in each mode constant, so commands which leave the tty in a confused state do not interfere with the shell. The shell also matches changes in the speed and padding of the tty. The list of tty modes that are kept constant can be examined and modified with the _s_e_t_t_y builtin. Note that although the editor uses CBREAK mode (or its equivalent), it takes typed-ahead characters anyway. The _e_c_h_o_t_c, _s_e_t_t_c and _t_e_l_l_t_c commands can be used to manipulate and debug terminal capabilities from the command line. On systems that support SIGWINCH or SIGWINDOW, the shell adapts to win- dow resizing automatically and adjusts the environment variables LLIINNEESS and CCOOLLUUMMNNSS if set. If the environment variable TTEERRMMCCAAPP contains li# and co# fields, the shell adjusts them to reflect the new window size. RREEFFEERREENNCCEE The next sections of this manual describe all of the available BBuuiillttiinn ccoommmmaannddss, SSppeecciiaall aalliiaasseess and SSppeecciiaall sshheellll vvaarriiaabblleess. BBuuiillttiinn ccoommmmaannddss %%_j_o_b A synonym for the _f_g builtin command. %%_j_o_b && A synonym for the _b_g builtin command. :: Does nothing, successfully. @@ @@ _n_a_m_e == _e_x_p_r @@ _n_a_m_e[_i_n_d_e_x] == _e_x_p_r @@ _n_a_m_e++++|---- @@ _n_a_m_e[_i_n_d_e_x]++++|---- The first form prints the values of all shell variables. The second form assigns the value of _e_x_p_r to _n_a_m_e. The third form assigns the value of _e_x_p_r to the _i_n_d_e_x'th component of _n_a_m_e; both _n_a_m_e and its _i_n_d_e_x'th component must already exist. _e_x_p_r may contain the operators `*', `+', etc., as in C. If _e_x_p_r contains `<', `>', `&' or `' then at least that part of _e_x_p_r must be placed within `()'. Note that the syntax of _e_x_p_r has nothing to do with that described under EExxpprreessssiioonnss. The fourth and fifth forms increment (`++') or decrement (`--') _n_a_m_e or its _i_n_d_e_x'th component. The space between `@' and _n_a_m_e is required. The spaces between _n_a_m_e and `=' and between `=' and _e_x_p_r are optional. Components of _e_x_p_r must be separated by spaces. aalliiaass [_n_a_m_e [_w_o_r_d_l_i_s_t]] Without arguments, prints all aliases. With _n_a_m_e, prints the alias for name. With _n_a_m_e and _w_o_r_d_l_i_s_t, assigns _w_o_r_d_l_i_s_t as the alias of _n_a_m_e. _w_o_r_d_l_i_s_t is command and filename substi- tuted. _n_a_m_e may not be `alias' or `unalias'. See also the _u_n_a_l_i_a_s builtin command. aalllloocc Shows the amount of dynamic memory acquired, broken down into used and free memory. With an argument shows the number of free and used blocks in each size category. The categories start at size 8 and double at each step. This command's output may vary across system types, because systems other than the VAX may use a different memory allocator. bbgg [%%_j_o_b ...] Puts the specified jobs (or, without arguments, the current job) into the background, continuing each if it is stopped. _j_o_b may be a number, a string, `', `%', `+' or `-' as described under JJoobbss. bbiinnddkkeeyy [--ll|--dd|--ee|--vv|--uu] (+) bbiinnddkkeeyy [--aa] [--bb] [--kk] [--rr] [----] _k_e_y (+) bbiinnddkkeeyy [--aa] [--bb] [--kk] [--cc|--ss] [----] _k_e_y _c_o_m_m_a_n_d (+) Without options, the first form lists all bound keys and the editor command to which each is bound, the second form lists the editor command to which _k_e_y is bound and the third form binds the editor command _c_o_m_m_a_n_d to _k_e_y. Options include: --ll Lists all editor commands and a short description of each. --dd Binds all keys to the standard bindings for the default editor. --ee Binds all keys to the standard GNU Emacs-like bindings. --vv Binds all keys to the standard _v_i(1)-like bindings. --aa Lists or changes key-bindings in the alternative key map. This is the key map used in _v_i command mode. --bb _k_e_y is interpreted as a control character written ^_c_h_a_r_a_c_- _t_e_r (e.g., `^A') or C-_c_h_a_r_a_c_t_e_r (e.g., `C-A'), a meta char- acter written M-_c_h_a_r_a_c_t_e_r (e.g., `M-A'), a function key written F-_s_t_r_i_n_g (e.g., `F-string'), or an extended prefix key written X-_c_h_a_r_a_c_t_e_r (e.g., `X-A'). --kk _k_e_y is interpreted as a symbolic arrow key name, which may be one of `down', `up', `left' or `right'. --rr Removes _k_e_y's binding. Be careful: `bindkey -r' does _n_o_t bind _k_e_y to _s_e_l_f_-_i_n_s_e_r_t_-_c_o_m_m_a_n_d (q.v.), it unbinds _k_e_y com- pletely. --cc _c_o_m_m_a_n_d is interpreted as a builtin or external command instead of an editor command. --ss _c_o_m_m_a_n_d is taken as a literal string and treated as termi- nal input when _k_e_y is typed. Bound keys in _c_o_m_m_a_n_d are themselves reinterpreted, and this continues for ten levels of interpretation. ---- Forces a break from option processing, so the next word is taken as _k_e_y even if it begins with '-'. --uu (or any invalid option) Prints a usage message. _k_e_y may be a single character or a string. If a command is bound to a string, the first character of the string is bound to _s_e_q_u_e_n_c_e_-_l_e_a_d_-_i_n and the entire string is bound to the com- mand. Control characters in _k_e_y can be literal (they can be typed by preceding them with the editor command _q_u_o_t_e_d_-_i_n_s_e_r_t, normally bound to `^V') or written caret-character style, e.g., `^A'. Delete is written `^?' (caret-question mark). _k_e_y and _c_o_m_m_a_n_d can contain backslashed escape sequences (in the style of Sys- tem V _e_c_h_o(1)) as follows: \\aa Bell \\bb Backspace \\ee Escape \\ff Form feed \\nn Newline \\rr Carriage return \\tt Horizontal tab \\vv Vertical tab \\_n_n_n The ASCII character corresponding to the octal num- ber _n_n_n `\' nullifies the special meaning of the following character, if it has any, notably `\' and `^'. bbss22ccmmdd _b_s_2_0_0_0_-_c_o_m_m_a_n_d (+) Passes _b_s_2_0_0_0_-_c_o_m_m_a_n_d to the BS2000 command interpreter for execution. Only non-interactive commands can be executed, and it is not possible to execute any command that would overlay the image of the current process, like /EXECUTE or /CALL-PROCE- DURE. (BS2000 only) bbrreeaakk Causes execution to resume after the _e_n_d of the nearest enclos- ing _f_o_r_e_a_c_h or _w_h_i_l_e. The remaining commands on the current line are executed. Multi-level breaks are thus possible by writing them all on one line. bbrreeaakkssww Causes a break from a _s_w_i_t_c_h, resuming after the _e_n_d_s_w. bbuuiillttiinnss (+) Prints the names of all builtin commands. bbyyee (+) A synonym for the _l_o_g_o_u_t builtin command. Available only if the shell was so compiled; see the vveerrssiioonn shell variable. ccaassee _l_a_b_e_l:: A label in a _s_w_i_t_c_h statement as discussed below. ccdd [--pp] [--ll] [--nn|--vv] [_n_a_m_e] If a directory _n_a_m_e is given, changes the shell's working directory to _n_a_m_e. If not, changes to hhoommee. If _n_a_m_e is `-' it is interpreted as the previous working directory (see OOtthheerr ssuubbssttiittuuttiioonnss). (+) If _n_a_m_e is not a subdirectory of the cur- rent directory (and does not begin with `/', `./' or `../'), each component of the variable ccddppaatthh is checked to see if it has a subdirectory _n_a_m_e. Finally, if all else fails but _n_a_m_e is a shell variable whose value begins with `/', then this is tried to see if it is a directory. With --pp, prints the final directory stack, just like _d_i_r_s. The --ll, --nn and --vv flags have the same effect on _c_d as on _d_i_r_s, and they imply --pp. (+) See also the iimmpplliicciittccdd shell variable. cchhddiirr A synonym for the _c_d builtin command. ccoommpplleettee [_c_o_m_m_a_n_d [_w_o_r_d//_p_a_t_t_e_r_n//_l_i_s_t[::_s_e_l_e_c_t]//[[_s_u_f_f_i_x]//] ...]] (+) Without arguments, lists all completions. With _c_o_m_m_a_n_d, lists completions for _c_o_m_m_a_n_d. With _c_o_m_m_a_n_d and _w_o_r_d etc., defines completions. _c_o_m_m_a_n_d may be a full command name or a glob-pattern (see FFiillee-- nnaammee ssuubbssttiittuuttiioonn). It can begin with `-' to indicate that completion should be used only when _c_o_m_m_a_n_d is ambiguous. _w_o_r_d specifies which word relative to the current word is to be completed, and may be one of the following: cc Current-word completion. _p_a_t_t_e_r_n is a glob-pattern which must match the beginning of the current word on the command line. _p_a_t_t_e_r_n is ignored when completing the current word. CC Like cc, but includes _p_a_t_t_e_r_n when completing the cur- rent word. nn Next-word completion. _p_a_t_t_e_r_n is a glob-pattern which must match the beginning of the previous word on the command line. NN Like nn, but must match the beginning of the word two before the current word. pp Position-dependent completion. _p_a_t_t_e_r_n is a numeric range, with the same syntax used to index shell vari- ables, which must include the current word. _l_i_s_t, the list of possible completions, may be one of the fol- lowing: aa Aliases bb Bindings (editor commands) cc Commands (builtin or external commands) CC External commands which begin with the supplied path prefix dd Directories DD Directories which begin with the supplied path pre- fix ee Environment variables ff Filenames FF Filenames which begin with the supplied path prefix gg Groupnames jj Jobs ll Limits nn Nothing ss Shell variables SS Signals tt Plain (``text'') files TT Plain (``text'') files which begin with the sup- plied path prefix vv Any variables uu Usernames xx Like nn, but prints _s_e_l_e_c_t when _l_i_s_t_-_c_h_o_i_c_e_s is used. XX Completions $_v_a_r Words from the variable _v_a_r (...) Words from the given list `...` Words from the output of command _s_e_l_e_c_t is an optional glob-pattern. If given, words from only _l_i_s_t that match _s_e_l_e_c_t are considered and the ffiiggnnoorree shell variable is ignored. The last three types of completion may not have a _s_e_l_e_c_t pattern, and xx uses _s_e_l_e_c_t as an explanatory message when the _l_i_s_t_-_c_h_o_i_c_e_s editor command is used. _s_u_f_f_i_x is a single character to be appended to a successful completion. If null, no character is appended. If omitted (in which case the fourth delimiter can also be omitted), a slash is appended to directories and a space to other words. Now for some examples. Some commands take only directories as arguments, so there's no point completing plain files. > complete cd 'p/1/d/' completes only the first word following `cd' (`p/1') with a directory. pp-type completion can also be used to narrow down command completion: > co[^D] complete compress > complete -co* 'p/0/(compress)/' > co[^D] > compress This completion completes commands (words in position 0, `p/0') which begin with `co' (thus matching `co*') to `compress' (the only word in the list). The leading `-' indicates that this completion is to be used with only ambiguous commands. > complete find 'n/-user/u/' is an example of nn-type completion. Any word following `find' and immediately following `-user' is completed from the list of users. > complete cc 'c/-I/d/' demonstrates cc-type completion. Any word following `cc' and beginning with `-I' is completed as a directory. `-I' is not taken as part of the directory because we used lowercase cc. Different _l_i_s_ts are useful with different commands. > complete alias 'p/1/a/' > complete man 'p/*/c/' > complete set 'p/1/s/' > complete true 'p/1/x:Truth has no options./' These complete words following `alias' with aliases, `man' with commands, and `set' with shell variables. `true' doesn't have any options, so xx does nothing when completion is attempted and prints `Truth has no options.' when completion choices are listed. Note that the _m_a_n example, and several other examples below, could just as well have used 'c/*' or 'n/*' as 'p/*'. Words can be completed from a variable evaluated at completion time, > complete ftp 'p/1/$hostnames/' > set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu) > ftp [^D] rtfm.mit.edu tesla.ee.cornell.edu > ftp [^C] > set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net) > ftp [^D] rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net or from a command run at completion time: > complete kill 'p/*/`ps | awk \{print\ \$1\}`/' > kill -9 [^D] 23113 23377 23380 23406 23429 23529 23530 PID Note that the _c_o_m_p_l_e_t_e command does not itself quote its argu- ments, so the braces, space and `$' in `{print $1}' must be quoted explicitly. One command can have multiple completions: > complete dbx 'p/2/(core)/' 'p/*/c/' completes the second argument to `dbx' with the word `core' and all other arguments with commands. Note that the positional completion is specified before the next-word completion. Because completions are evaluated from left to right, if the next-word completion were specified first it would always match and the positional completion would never be executed. This is a common mistake when defining a completion. The _s_e_l_e_c_t pattern is useful when a command takes files with only particular forms as arguments. For example, > complete cc 'p/*/f:*.[cao]/' completes `cc' arguments to files ending in only `.c', `.a', or `.o'. _s_e_l_e_c_t can also exclude files, using negation of a glob- pattern as described under FFiilleennaammee ssuubbssttiittuuttiioonn. One might use > complete rm 'p/*/f:^*.{c,h,cc,C,tex,1,man,l,y}/' to exclude precious source code from `rm' completion. Of course, one could still type excluded names manually or over- ride the completion mechanism using the _c_o_m_p_l_e_t_e_-_w_o_r_d_-_r_a_w or _l_i_s_t_-_c_h_o_i_c_e_s_-_r_a_w editor commands (q.v.). The `C', `D', `F' and `T' _l_i_s_ts are like `c', `d', `f' and `t' respectively, but they use the _s_e_l_e_c_t argument in a different way: to restrict completion to files beginning with a particu- lar path prefix. For example, the Elm mail program uses `=' as an abbreviation for one's mail directory. One might use > complete elm c@=@F:$HOME/Mail/@ to complete `elm -f =' as if it were `elm -f ~/Mail/'. Note that we used `@' instead of `/' to avoid confusion with the _s_e_l_e_c_t argument, and we used `$HOME' instead of `~' because home directory substitution works at only the beginning of a word. _s_u_f_f_i_x is used to add a nonstandard suffix (not space or `/' for directories) to completed words. > complete finger 'c/*@/$hostnames/' 'p/1/u/@' completes arguments to `finger' from the list of users, appends an `@', and then completes after the `@' from the `hostnames' variable. Note again the order in which the completions are specified. Finally, here's a complex example for inspiration: > complete find \ 'n/-name/f/' 'n/-newer/f/' 'n/-{,n}cpio/f/' \ 'n/-exec/c/' 'n/-ok/c/' 'n/-user/u/' \ 'n/-group/g/' 'n/-fstype/(nfs 4.2)/' \ 'n/-type/(b c d f l p s)/' \ 'c/-/(name newer cpio ncpio exec ok user \ group fstype type atime ctime depth inum \ ls mtime nogroup nouser perm print prune \ size xdev)/' \ 'p/*/d/' This completes words following `-name', `-newer', `-cpio' or `ncpio' (note the pattern which matches both) to files, words following `-exec' or `-ok' to commands, words following `user' and `group' to users and groups respectively and words follow- ing `-fstype' or `-type' to members of the given lists. It also completes the switches themselves from the given list (note the use of cc-type completion) and completes anything not otherwise completed to a directory. Whew. Remember that programmed completions are ignored if the word being completed is a tilde substitution (beginning with `~') or a variable (beginning with `$'). _c_o_m_p_l_e_t_e is an experimental feature, and the syntax may change in future versions of the shell. See also the _u_n_c_o_m_p_l_e_t_e builtin command. ccoonnttiinnuuee Continues execution of the nearest enclosing _w_h_i_l_e or _f_o_r_e_a_c_h. The rest of the commands on the current line are executed. ddeeffaauulltt:: Labels the default case in a _s_w_i_t_c_h statement. It should come after all _c_a_s_e labels. ddiirrss [--ll] [--nn|--vv] ddiirrss --SS|--LL [_f_i_l_e_n_a_m_e] (+) ddiirrss --cc (+) The first form prints the directory stack. The top of the stack is at the left and the first directory in the stack is the current directory. With --ll, `~' or `~_n_a_m_e' in the output is expanded explicitly to hhoommee or the pathname of the home directory for user _n_a_m_e. (+) With --nn, entries are wrapped before they reach the edge of the screen. (+) With --vv, entries are printed one per line, preceded by their stack positions. (+) If more than one of --nn or --vv is given, --vv takes precedence. --pp is accepted but does nothing. With --SS, the second form saves the directory stack to _f_i_l_e_n_a_m_e as a series of _c_d and _p_u_s_h_d commands. With --LL, the shell sources _f_i_l_e_n_a_m_e, which is presumably a directory stack file saved by the --SS option or the ssaavveeddiirrss mechanism. In either case, ddiirrssffiillee is used if _f_i_l_e_n_a_m_e is not given and _~_/_._c_s_h_d_i_r_s is used if ddiirrssffiillee is unset. Note that login shells do the equivalent of `dirs -L' on startup and, if ssaavveeddiirrss is set, `dirs -S' before exiting. Because only _~_/_._t_c_s_h_r_c is normally sourced before _~_/_._c_s_h_d_i_r_s, ddiirrssffiillee should be set in _~_/_._t_c_s_h_r_c rather than _~_/_._l_o_g_i_n. The last form clears the directory stack. eecchhoo [--nn] _w_o_r_d ... Writes each _w_o_r_d to the shell's standard output, separated by spaces and terminated with a newline. The eecchhoo__ssttyyllee shell variable may be set to emulate (or not) the flags and escape sequences of the BSD and/or System V versions of _e_c_h_o; see _e_c_h_o(1). eecchhoottcc [--ssvv] _a_r_g ... (+) Exercises the terminal capabilities (see _t_e_r_m_c_a_p(5)) in _a_r_g_s. For example, 'echotc home' sends the cursor to the home posi- tion, 'echotc cm 3 10' sends it to column 3 and row 10, and 'echotc ts 0; echo "This is a test."; echotc fs' prints "This is a test." in the status line. If _a_r_g is 'baud', 'cols', 'lines', 'meta' or 'tabs', prints the value of that capability ("yes" or "no" indicating that the terminal does or does not have that capability). One might use this to make the output from a shell script less verbose on slow terminals, or limit command output to the number of lines on the screen: > set history=`echotc lines` > @ history-- Termcap strings may contain wildcards which will not echo cor- rectly. One should use double quotes when setting a shell variable to a terminal capability string, as in the following example that places the date in the status line: > set tosl="`echotc ts 0`" > set frsl="`echotc fs`" > echo -n "$tosl";date; echo -n "$frsl" With --ss, nonexistent capabilities return the empty string rather than causing an error. With --vv, messages are verbose. eellssee eenndd eennddiiff eennddssww See the description of the _f_o_r_e_a_c_h, _i_f, _s_w_i_t_c_h, and _w_h_i_l_e statements below. eevvaall _a_r_g ... Treats the arguments as input to the shell and executes the resulting command(s) in the context of the current shell. This is usually used to execute commands generated as the result of command or variable substitution, because parsing occurs before these substitutions. See _t_s_e_t(1) for a sample use of _e_v_a_l. eexxeecc _c_o_m_m_a_n_d Executes the specified command in place of the current shell. eexxiitt [_e_x_p_r] The shell exits either with the value of the specified _e_x_p_r (an expression, as described under EExxpprreessssiioonnss) or, without _e_x_p_r, with the value of the ssttaattuuss variable. ffgg [%%_j_o_b ...] Brings the specified jobs (or, without arguments, the current job) into the foreground, continuing each if it is stopped. _j_o_b may be a number, a string, `', `%', `+' or `-' as described under JJoobbss. See also the _r_u_n_-_f_g_-_e_d_i_t_o_r editor command. ffiilleetteesstt --_o_p _f_i_l_e ... (+) Applies _o_p (which is a file inquiry operator as described under FFiillee iinnqquuiirryy ooppeerraattoorrss) to each _f_i_l_e and returns the results as a space-separated list. ffoorreeaacchh _n_a_m_e ((_w_o_r_d_l_i_s_t)) ... eenndd Successively sets the variable _n_a_m_e to each member of _w_o_r_d_l_i_s_t and executes the sequence of commands between this command and the matching _e_n_d. (Both _f_o_r_e_a_c_h and _e_n_d must appear alone on separate lines.) The builtin command _c_o_n_t_i_n_u_e may be used to continue the loop prematurely and the builtin command _b_r_e_a_k to terminate it prematurely. When this command is read from the terminal, the loop is read once prompting with `foreach? ' (or pprroommpptt22) before any statements in the loop are executed. If you make a mistake typing in a loop at the terminal you can rub it out. ggeettssppaatthh (+) Prints the system execution path. (TCF only) ggeettxxvveerrss (+) Prints the experimental version prefix. (TCF only) gglloobb _w_o_r_d_l_i_s_t Like _e_c_h_o, but no `\' escapes are recognized and words are delimited by null characters in the output. Useful for pro- grams which wish to use the shell to filename expand a list of words. ggoottoo _w_o_r_d _w_o_r_d is filename and command-substituted to yield a string of the form `label'. The shell rewinds its input as much as pos- sible, searches for a line of the form `label:', possibly pre- ceded by blanks or tabs, and continues execution after that line. hhaasshhssttaatt Prints a statistics line indicating how effective the internal hash table has been at locating commands (and avoiding _e_x_e_c's). An _e_x_e_c is attempted for each component of the ppaatthh where the hash function indicates a possible hit, and in each component which does not begin with a `/'. On machines without _v_f_o_r_k(2), prints only the number and size of hash buckets. hhiissttoorryy [--hhTTrr] [_n] hhiissttoorryy --SS|--LL||--MM [_f_i_l_e_n_a_m_e] (+) hhiissttoorryy --cc (+) The first form prints the history event list. If _n is given only the _n most recent events are printed or saved. With --hh, the history list is printed without leading numbers. If --TT is specified, timestamps are printed also in comment form. (This can be used to produce files suitable for loading with 'history -L' or 'source -h'.) With --rr, the order of printing is most recent first rather than oldest first. With --SS, the second form saves the history list to _f_i_l_e_n_a_m_e. If the first word of the ssaavveehhiisstt shell variable is set to a number, at most that many lines are saved. If the second word of ssaavveehhiisstt is set to `merge', the history list is merged with the existing history file instead of replacing it (if there is one) and sorted by time stamp. (+) Merging is intended for an environment like the X Window System with several shells in simultaneous use. Currently it succeeds only when the shells quit nicely one after another. With --LL, the shell appends _f_i_l_e_n_a_m_e, which is presumably a his- tory list saved by the --SS option or the ssaavveehhiisstt mechanism, to the history list. --MM is like --LL, but the contents of _f_i_l_e_n_a_m_e are merged into the history list and sorted by timestamp. In either case, hhiissttffiillee is used if _f_i_l_e_n_a_m_e is not given and _~_/_._h_i_s_t_o_r_y is used if hhiissttffiillee is unset. `history -L' is exactly like 'source -h' except that it does not require a filename. Note that login shells do the equivalent of `history -L' on startup and, if ssaavveehhiisstt is set, `history -S' before exiting. Because only _~_/_._t_c_s_h_r_c is normally sourced before _~_/_._h_i_s_t_o_r_y, hhiissttffiillee should be set in _~_/_._t_c_s_h_r_c rather than _~_/_._l_o_g_i_n. If hhiissttlliitt is set, the first and second forms print and save the literal (unexpanded) form of the history list. The last form clears the history list. hhuupp [_c_o_m_m_a_n_d] (+) With _c_o_m_m_a_n_d, runs _c_o_m_m_a_n_d such that it will exit on a hangu