bsh(1) bsh(1) NAME bsh, jsh - shell, the standard/job control command programming language SYNOPSIS bsh [ -acefhiknprstuvx ] [ args ] jsh [ -acefhiknprstuvx ] [ args ] DESCRIPTION Note: This is the Bourne shell description. All references to sh and shell pertain to bsh and all references below to /usr/lib/rsh, the restricted shell, no longer apply to the Bourne shell. (See sh(1)). bsh is a command programming language that executes commands read from a terminal or a file. jsh is an interface to the shell that provides all the functionality of sh and enables Job Control (see Job Control below). See Invocation below for the meaning of arguments to the shell. See CAVEATS below for interaction with Korn shell builtins. Definitions A blank is a tab or a space. A name is a sequence of letters, digits, or underscores beginning with a letter or underscore. A parameter is a name, a digit, or any of the characters *, @, #, ?, -, $, and ! . Commands A simple-command is a sequence of non-blank words separated by blanks. The first word specifies the name of the command to be executed. Except as specified below, the remaining words are passed as arguments to the invoked command. The command name is passed as argument 0 (see exec(2)). The value of a simple-command is its exit status if it terminates normally, or (octal) 200+status if it terminates abnormally (see signal(2) for a list of status values). A pipeline is a sequence of one or more commands separated by |. The standard output of each command but the last is connected by a pipe(2) to the standard input of the next command. Each command is run as a separate process; the shell waits for the last command to terminate. The exit status of a pipeline is the exit status of the last command. A list is a sequence of one or more pipelines separated by ;, &, &&, or ||, and optionally terminated by ; or &. Of these four symbols, ; and & have equal precedence, which is lower than that of && and ||. The symbols && and || also have equal precedence. A semicolon (;) causes sequential execution of the preceding pipeline; an ampersand (&) causes asynchronous execution of the preceding pipeline (that is, the shell does not wait for that pipeline to finish). The symbol && (||) causes the list following it to be executed only if the preceding pipeline returns a zero (nonzero) exit status. An arbitrary number of newlines can appear in a list, instead of semicolons, to delimit commands. A command is either a simple-command or one of the following. Unless otherwise stated, the value returned by a command is that of the last simple-command executed in the command. for name [ in word ... ] do list done Each time a for command is executed, name is set to the next word taken from the in word list. If in word ... is omitted, the for command executes the do list once for each positional parameter that is set (see Parameter Substitution below). Execution ends when there are no more words in the list. case word in [ pattern [ | pattern ] ...) list ;; ] ... esac A case command executes the list associated with the first pattern that matches word. The form of the patterns is the same as that used for filename generation (see Filename Generation) except that a slash, a leading dot, or a dot immediately following a slash need not be matched explicitly. if list then list [ elif list then list ] ... [ else list ] fi The list following if is executed and, if it returns a zero exit status, the list following the first then is executed. Otherwise, the list following elif is executed and, if its value is zero, the list following the next then is executed. Failing that, the else list is executed. If no else list or then list is executed, the if command returns a zero exit status. while list do list done A while command repeatedly executes the while list and, if the exit status of the last command in the list is zero, executes the do list; otherwise the loop terminates. If no commands in the do list are executed, the while command returns a zero exit status; until can be used in place of while to negate the loop termination test. (list) Execute list in a subshell. {list;} list is executed in the current (that is, parent) shell. The { must be followed by a space. name () {list;} Define a function that is referenced by name. The body of the function is the list of commands between { and }. The list can appear on the same line as the {. If it does, the { and list must be separated by a space. The } cannot be on the same line as list; it must be on a newline. Execution of functions is described below (see Execution). The { and } are unnecessary if the body of the function is a command as defined above, under Commands. The following words are only recognized as the first word of a command and when not quoted: if then else elif fi case esac for while until do done { } Comments A word beginning with # causes that word and all the following characters up to a newline to be ignored. Command Substitution The shell reads commands from the string between two grave accents (``) and the standard output from these commands can be used as all or part of a word. Trailing newlines from the standard output are removed. No interpretation is done on the string before the string is read, except to remove backslashes (\) used to escape other characters. Backslashes can be used to escape a grave accent (`) or another backslash (\) and are removed before the command string is read. Escaping grave accents allows nested command substitution. If the command substitution lies within a pair of double quotes (" ... `...` ... "), a backslash used to escape a double quote (\") is removed; otherwise, it is left intact. If a backslash is used to escape a newline character (\newline), both the backslash and the newline are removed (see the later section on "Quoting"). In addition, backslashes used to escape dollar signs (\$) are removed. Since no interpretation is done on the command string before it is read, inserting a backslash to escape a dollar sign has no effect. Backslashes that precede characters other than \, `, ", newline, and $ are left intact when the command string is read. Parameter Substitution The character $ is used to introduce substitutable parameters. There are two types of parameters, positional and keyword. If parameter is a digit, it is a positional parameter. Positional parameters can be assigned values by set. Keyword parameters (also known as variables) can be assigned values by writing: name = value [ name = value ] ... Pattern-matching is not performed on value. There cannot be a function and a variable with the same name. ${parameter} The value, if any, of the parameter is substituted. The braces are required only when parameter is followed by a letter, digit, or underscore that is not to be interpreted as part of its name. If parameter is * or @, all the positional parameters, starting with $1, are substituted (separated by spaces). Parameter $0 is set from argument zero when the shell is invoked. ${parameter:-word} If parameter is set and is non-null, substitute its value; otherwise substitute word. ${parameter:=word} If parameter is not set or is null set it to word; the value of the parameter is substituted. Positional parameters cannot be assigned to in this way. ${parameter:?word} If parameter is set and is non-null, substitute its value; otherwise, print word and exit from the shell. If word is omitted, the message "parameter null or not set" is printed. ${parameter:+word} If parameter is set and is non-null, substitute word; otherwise substitute nothing. In the above, word is not evaluated unless it is to be used as the substituted string, so that, in the following example, pwd is executed only if d is not set or is null: echo ${d:-`pwd`} If the colon (:) is omitted from the above expressions, the shell only checks whether parameter is set or not. The following parameters are automatically set by the shell: * Expands to the positional parameters, beginning with 1. @ Expands to the positional parameters beginning with 1, except when expanded within double quotes, in which case each positional parameter expands as a separate field. # The number of positional parameters in decimal. - Flags supplied to the shell on invocation or by the set command. ? The decimal value returned by the last synchronously executed command. $ The process number of this shell. $ reports the process ID of the parent shell in all shell constructs, including pipelines, and in parenthesized subshells. ! The process number of the last background command invoked. The following parameters are used by the shell: HOME The default argument (home directory) for the cd command, set to the user's login directory by login(1) from the password file (see passwd(4)). PATH The search path for commands (see Execution below). The user cannot change PATH if executing under rsh. CDPATH The search path for the cd command. MAIL If this parameter is set to the name of a mail file and the MAILPATH parameter is not set, the shell informs the user of the arrival of mail in the specified file. MAILCHECK This parameter specifies how often (in seconds) the shell checks for the arrival of mail in the files specified by the MAILPATH or MAIL parameters. The default value is 600 seconds (10 minutes). If set to 0, the shell checks before each prompt. MAILPATH A colon (:) separated list of filenames. If this parameter is set, the shell informs the user of the arrival of mail in any of the specified files. Each filename can be followed by % and a message to be printed when the modification time changes. The default message is "you have mail". PS1 Primary prompt string, by default ``$ ''. PS2 Secondary prompt string, by default ``> ''. IFS Internal field separators, normally space, tab, and newline. SHACCT If this parameter is set to the name of a file writable by the user, the shell writes an accounting record in the file for each shell procedure executed. SHELL When the shell is invoked, it scans the environment (see Environment below) for this name. If it is found and 'rsh' is the filename part of its value, the shell becomes a restricted shell. The shell gives default values to PATH, PS1, PS2, MAILCHECK, and IFS. HOME and MAIL are set by login(1). Blank Interpretation After parameter and command substitution, the results of substitution are scanned for internal field separator characters (those found in IFS) and split into distinct arguments where such characters are found. Explicit null arguments ("" or '') are retained. Implicit null arguments (those resulting from parameters that have no values) are removed. The original whitespace characters (space, tab, and newline) are always considered internal field separators. Input/Output A command's input and output can be redirected using a special notation interpreted by the shell. The following can appear anywhere in a simple-command or can precede or follow a command and are not passed on as arguments to the invoked command. Note that parameter and command substitution occurs before word or digit is used. <word Use file word as standard input (file descriptor 0). >word Use file word as standard output (file descriptor 1). If the file does not exist it is created; otherwise, it is truncated to zero length. >>word Use file word as standard output. If the file exists output is appended to it (by first seeking to the end-of-file); otherwise, the file is created. <<[-]word After parameter and command substitution is done on word, the shell input is read up to the first line that literally matches the resulting word, or to an end-of-file. If, however, - is appended to <<: 1. Leading tabs are stripped from word before the shell input is read (but after parameter and command substitution is done on word). 2. Leading tabs are stripped from the shell input as it is read and before each line is compared with word. 3. Shell input is read up to the first line that literally matches the resulting word, or to an end-of-file. If any character of word is quoted (see Quoting, later), no additional processing is done to the shell input. If no characters of word are quoted: 1. Parameter and command substitution occurs. 2. (Escaped) \newline is ignored. 3. \ must be used to quote the characters \, $, and `. The resulting document becomes the standard input. <&digit Use the file associated with file descriptor digit as standard input. Similarly for the standard output using >&digit. <&- The standard input is closed. Similarly for the standard output using >&-. If any of the above is preceded by a digit, the file descriptor that will be associated with the file is that specified by the digit (instead of the default 0 or 1). For example: ... 2>&1 associates file descriptor 2 with the file currently associated with file descriptor 1. The order in which redirections are specified is significant. The shell evaluates redirections left-to-right. For example: ... 1>xxx 2>&1 first associates file descriptor 1 with file xxx. It associates file descriptor 2 with the file associated with file descriptor 1 (that is, xxx). If the order of redirections were reversed, file descriptor 2 would be associated with the terminal (assuming file descriptor 1 had been) and file descriptor 1 would be associated with file xxx. Using the terminology introduced on the first page, under Commands, if a command is composed of several simple commands, redirection is evaluated for the entire command before it is evaluated for each simple command. That is, the shell evaluates redirection for the entire list, then each pipeline within the list, then each command within each pipeline, then each list within each command. If a command is followed by & the default standard input for the command is the empty file /dev/null. Otherwise, the environment for the execution of a command contains the file descriptors of the invoking shell as modified by input/output specifications. Redirection of output is not allowed in the restricted shell. Filename Generation Before a command is executed, each command word is scanned for the characters *, ?, and [. If one of these characters appears the word is regarded as a pattern. The word is replaced with alphabetically sorted filenames that match the pattern. If no filename is found that matches the pattern, the word is left unchanged. The character . at the start of a filename or immediately following a /, as well as the character / itself, must be matched explicitly. * Matches any string, including the null string. ? Matches any single character. [...] Matches any one of the enclosed characters. A pair of characters separated by - matches any character lexically between the pair, inclusive. If the first character following the opening [ is a !, any character not enclosed is matched. Quoting The following characters have a special meaning to the shell and cause termination of a word unless quoted: ; & ( ) | ^ < > newline space tab A character can be quoted that is, made to stand for itself) by preceding it with a backslash (\) or inserting it between a pair of quote marks ('' or ""). During processing, the shell can quote certain characters to prevent them from taking on a special meaning. Backslashes used to quote a single character are removed from the word before the command is executed. The pair \newline is removed from a word before command and parameter substitution. All characters enclosed between a pair of single quote marks (''), except a single quote, are quoted by the shell. Backslash has no special meaning inside a pair of single quotes. A single quote can be quoted inside a pair of double quote marks (for example, "'"). Inside a pair of double quote marks (""), parameter and command substitution occurs and the shell quotes the results to avoid blank interpretation and filename generation. If $* is within a pair of double quotes, the positional parameters are substituted and quoted, separated by quoted spaces ("$1 $2 ..."); however, if $@ is within a pair of double quotes, the positional parameters are substituted and quoted, separated by unquoted spaces ("$1" "$2" ...). \ quotes the characters \, `, ", and $. The pair \newline is removed before parameter and command substitution. If a backslash precedes characters other than \, `, ", $, and newline, then the backslash itself is quoted by the shell. Prompting When used interactively, the shell prompts with the value of PS1 before reading a command. If at any time a newline is typed and further input is needed to complete a command, the secondary prompt that is, the value of PS2) is issued. Environment The environment (see environ(5)) is a list of name-value pairs that is passed to an executed program in the same way as a normal argument list. The shell interacts with the environment in several ways. On invocation, the shell scans the environment and creates a parameter for each name found, giving it the corresponding value. If the user modifies the value of any of these parameters or creates new parameters, none of these affects the environment unless the export command is used to bind the shell's parameter to the environment (see also set -a). A parameter can be removed from the environment with the unset command. The environment seen by any executed command is thus composed of any unmodified name- value pairs originally inherited by the shell, minus any pairs removed by unset, plus any modifications or additions, all of which must be noted in export commands. The environment for any simple-command can be augmented by prefixing it with one or more assignments to parameters. Thus these two commands are equivalent (as far as the execution of cmd is concerned if cmd is not a Special Command): TERM=450 cmd (export TERM; TERM=450; cmd) If cmd is a Special Command, then TERM=45 cmd modifies the TERM variable in the current shell. If the -k flag is set, all keyword arguments are placed in the environment, even if they occur after the command name. The following first prints a=b c and c: echo a=b c set -k echo a=b c Signals When a command is run in the background (cmd &) under sh, it can receive INTERRUPT and QUIT signals but ignores them by default. (A background process can override this default behavior via trap or signal. For details, see the description of trap, below, or signal(2).) When a command is run in the background under jsh, however, it does not receive INTERRUPT or QUIT signals. Otherwise signals have the values inherited by the shell from its parent, with the exception of signal 11 (SIGSEGV). See also the trap command below. Execution Each time a command is executed, the command substitution, parameter substitution, blank interpretation, input/output redirection, and filename generation listed above are carried out. If the command name matches the name of a defined function, the function is executed in the shell process (note how this differs from the execution of shell procedures). If the command name does not match the name of a defined function, but matches one of the Special Commands listed below, it is executed in the shell process. The positional parameters $1, $2, and so on are set to the arguments of the function. If the command name matches neither a Special Command nor the name of a defined function, a new process is created and an attempt is made to execute the command via exec(2). The shell parameter PATH defines the search path for the directory containing the command. Alternative directory names are separated by a colon (:). The default path is: :/usr/sbin:/usr/bsd:/bin:/usr/bin:/usr/bin/X11 specifying the current directory, /usr/sbin, /usr/bsd, /bin, /usr/bin, and /usr/bin/X11, in that order. Note that the current directory is specified by a null pathname. It can appear immediately after the equal sign, between two colon delimiters anywhere in the path list, or at the end of the path list. If the command name contains a / the search path is not used; such commands are not executed by the restricted shell. Otherwise, each directory in the path is searched for an executable file. If the file has execute permission but is not an a.out file, it is assumed to be a file containing shell commands. A subshell is spawned to read it. A parenthesized command is also executed in a subshell. The location in the search path where a command was found is remembered by the shell (to help avoid unnecessary execs later). If the command was found in a relative directory, its location must be re-determined whenever the current directory changes. The shell forgets all remembered locations whenever the PATH variable is changed or the hash -r command is executed (see below). Special Commands Input/output redirection is now permitted for these commands. File descriptor 1 is the default output location. When Job Control is enabled, additional Special Commands are added to the shell's environment (see Job Control). : No effect; the command does nothing. A zero exit code is returned. . file Read and execute commands from file and return. The search path specified by PATH is used to find the directory containing file. break [ n ] Exit from the enclosing for or while loop, if any. If n is specified break n levels. continue [ n ] Resume the next iteration of the enclosing for or while loop. If n is specified resume at the n-th enclosing loop. cd [ arg ] Change the current directory to arg. The shell parameter HOME is the default arg. The shell parameter CDPATH defines the search path for the directory containing arg. Alternative directory names are separated by a colon (:). The default path is <null> (specifying the current directory). Note that the current directory is specified by a null pathname. It can appear immediately after the equal sign or between the colon delimiters anywhere else in the path list. If arg begins with a / the search path is not used. Otherwise, each directory in the path is searched for arg. The cd command cannot be executed by rsh. echo [ arg ... ] Echo arguments. See echo(1) for usage and description. eval [ arg ... ] The arguments are read as input to the shell and the resulting command(s) executed. exec [ arg ... ] The command specified by the arguments is executed in place of this shell without creating a new process. Input/output arguments can appear and, if no other arguments are given, cause the shell input/output to be modified. exit [ n ] Causes a shell to exit with the exit status specified by n. If n is omitted, the exit status is that of the last command executed (an end-of-file also causes the shell to exit.) export [ name ... ] The given names are marked for automatic export to the environment of subsequently-executed commands. If no arguments are given, variable names that have been marked for export during the current shell's execution are listed. (Variable names exported from a parent shell are listed only if they have been exported again during the current shell's execution.) Function names are not exported. getopts Use in shell scripts to support command syntax standards (see intro(1)); it parses positional parameters and checks for legal options. See getopts(1) for usage and description. hash [ -r ] [ name ... ] For each name, the location in the search path of the command specified by name is determined and remembered by the shell. The -r option causes the shell to forget all remembered locations. If no arguments are given, information about remembered commands is presented. hits is the number of times a command has been invoked by the shell process. cost is a measure of the work required to locate a command in the search path. If a command is found in a "relative" directory in the search path, after changing to that directory, the stored location of that command is recalculated. Commands for which this is done are indicated by an asterisk (*) adjacent to the hits information. cost is incremented when the recalculation is done. limit [ -h ] [ resource [maximum-use ] ] Limits the consumption by the current process and each process it creates to not individually exceed maximum-use on the specified resource. If no maximum-use is given, then the current limit is printed; if no resource is given, then all limitations are given. If the -h flag is given, the hard limits are used instead of the current limits. The hard limits impose a ceiling on the values of the current limits. Only the superuser can raise the hard limits, but a user can lower or raise the current limits within the legal range. Resources controllable currently include cputime, the maximum number of cpu-seconds to be used by each process, filesize, the largest single file that can be created, datasize, the maximum growth of the data region via sbrk(2) beyond the end of the program text, stacksize, the maximum size of the automatically-extended stack region, coredumpsize, the size of the largest core dump created, memoryuse, the maximum amount of physical memory a process can have allocated to it at a given time, descriptors, the maximum number of open files, and vmemory, the maximum total virtual size of the process, including text, data, heap, shared memory, mapped files, stack, and so on. The maximum-use can be given as a (floating point or integer) number followed by a scale factor. For all limits other than cputime the default scale is k or kilobytes (1024 bytes); a scale factor of m or megabytes can also be used. For cputime the default scaling is seconds, while m for minutes or h for hours, or a time of the form mm:ss giving minutes and seconds can be used. For both resource names and scale factors, unambiguous prefixes of the names suffice. newgrp [ arg ... ] Equivalent to exec newgrp arg .... See newgrp(1) for usage and description. pwd Print the current working directory. See pwd(1) for usage and description. read [ name ... ] One line is read from the standard input and, using the internal field separator, IFS (normally space or tab), to delimit word boundaries, the first word is assigned to the first name, the second word to the second name, and so on, with leftover words assigned to the last name. Lines can be continued using \newline. Characters other than newline can be quoted by preceding them with a backslash. These backslashes are removed before words are assigned to names, and no interpretation is done on the character that follows the backslash. The return code is 0 unless an end-of-file is encountered. readonly [ name ... ] The given names are marked readonly and the values of the these names cannot be changed by subsequent assignment. If no arguments are given, a list of all readonly names is printed. return [ n ] Causes a function to exit with the return value specified by n. If n is omitted, the return status is that of the last command executed. set [ --aefhkntuvx [ arg ... ] ] -a Mark variables that are modified or created for export. -e Exit immediately if a command exits with a nonzero exit status. -f Disable filename generation. -h Locate and remember function commands as functions are defined (function commands are normally located when the function is executed). -k All keyword arguments are placed in the environment for a command, not just those that precede the command name. -n Read commands but do not execute them. -t Exit after reading and executing one command. -u Treat unset variables as an error when substituting. -v Print shell input lines as they are read. -x Print commands and their arguments as they are executed. -- Do not change any of the flags; useful in setting $1 to -. Using + rather than - causes these flags to be turned off. These flags can also be used upon invocation of the shell. The current set of flags can be found in $-. The remaining arguments are positional parameters and are assigned, in order, to $1, $2, .... If no arguments are given the values of all names are printed. shift [ n ] The positional parameters from $n+1 ... are renamed $1 .... If n is not given, it is assumed to be 1. test Evaluate conditional expressions. See test(1) for usage and description. times Print the accumulated user and system times for processes run from the shell. trap [ arg ] [ n ] ... The command arg is to be read and executed when the shell receives signal(s) n. (Note that arg is scanned once when the trap is set and once when the trap is taken.) Trap commands are executed in order of signal number. Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective. An error results when an attempt is made to trap signal 11 (SIGSEGV--segmentation fault). If arg is absent all trap(s) n are reset to their original values. If arg is the null string this signal is ignored by the shell and by the commands it invokes. If n is 0 the command arg is executed on exit from the shell. The trap command with no arguments prints a list of commands associated with each signal number. type [ name ... ] For each name, indicate how it would be interpreted if used as a command name. ulimit [ n ] Impose a size limit of n blocks on files written by the shell and its child processes (files of any size can be read). If n is omitted, the current limit is printed. You can lower your own ulimit, but only a superuser (see su(1M)) can raise a ulimit. umask [ nnn ] The user file creation mask is set to nnn (see umask(1)). If nnn is omitted, the current value of the mask is printed. unlimit [ -h ] [ resource ] Removes the limitation on resource. If no resource is specified, then all resource limitations are removed. If -h is given, the corresponding hard limits are removed. Only the superuser can do this. unset [ name ... ] For each name, remove the corresponding variable or function. The variables PATH, PS1, PS2, MAILCHECK and IFS cannot be unset. wait [ n ] Wait for your background process whose process id is n and report its termination status. If n is omitted, all your shell's currently active background processes are waited for and the return code is zero. Invocation If the shell is invoked through exec(2) and the first character of argument zero is -, commands are initially read from /etc/profile and from $HOME/.profile, if such files exist. Thereafter, commands are read as described below, which is also the case when the shell is invoked as /bin/sh. The flags below are interpreted by the shell on invocation only; Note that unless the -c or -s flag is specified, the first argument is assumed to be the name of a file containing commands, and the remaining arguments are passed as positional parameters to that command file: -c string If the -c flag is present, commands are read from string. -s If the -s flag is present or if no arguments remain, commands are read from the standard input. Any remaining arguments specify the positional parameters. Shell output (except for Special Commands) is written to file descriptor 2. -i If the -i flag is present or if the shell input and output are attached to a terminal, this shell is interactive. In this case TERMINATE is ignored (so that kill 0 does not kill an interactive shell) and INTERRUPT is caught and ignored (so that wait is interruptible). In all cases, QUIT is ignored by the shell. -p If the -p flag is present, the shell skips the processing of the system profile (/etc/profile) and the user profile (.profile) when it starts. -r If the -r flag is present the shell is a restricted shell. The remaining flags and arguments are described under the set command above. Job Control (jsh) When the shell is invoked as jsh, Job Control is enabled in addition to all of the functionality described previously for sh. Typically Job Control is enabled for the interactive shell only. Noninteractive shells typically do not benefit from the added functionality of Job Control. With Job Control enabled every command or pipeline the user enters at the terminal is called a job. All jobs exist in one of the following states: foreground, background, or stopped. These terms are defined as follows: 1) a job in the foreground has read and write access to the controlling terminal; 2) a job in the background is denied read access and has conditional write access to the controlling terminal (see stty(1)); 3) a stopped job is a job that has been placed in a suspended state, usually as a result of a SIGTSTP signal (see signal(2)). Jobs in the foreground can be stopped by INTERRUPT or QUIT signals from the keyboard; background jobs cannot be stopped by these signals. Every job the shell starts is assigned a positive integer, called a job number, which is tracked by the shell and is used, later, as an identifier to indicate a specific job. Additionally the shell keeps track of the current and previous jobs. The current job is the most recent job to be started or restarted. The previous job is the first noncurrent job. The acceptable syntax for a Job Identifier is of the form: %jobid where jobid can be specified in any of the following formats: % or + For the current job. - For the previous job. ?string Specify the job for which the command line uniquely contains string. n For job number n, where n is a job number. pref Where pref is a unique prefix of the command name (for example, if the command ls -l foo were running in the background, it could be referred to as %ls); pref cannot contain blanks unless it is quoted. When Job Control is enabled, the following commands are added to the user's environment to manipulate jobs: bg [%jobid ...] Resumes the execution of a stopped job in the background. If %jobid is omitted the current job is assumed. fg [%jobid ...] Resumes the execution of a stopped job in the foreground, also moves an executing background job into the foreground. If %jobid is omitted the current job is assumed. jobs [-p|-l] [%jobid ...] jobs -x command [arguments] Reports all jobs that are stopped or executing in the background. If %jobid is omitted, all jobs that are stopped or running in the background are reported. The following options modify/enhance the output of jobs: -l Report the process group ID and working directory of the jobs. -p Report only the process group ID of the jobs. -x Replace any jobid found in command or arguments with the corresponding process group ID, and then execute command passing it arguments. kill [-signal] %jobid Builtin version of kill to provide the functionality of the kill command for processes identified with a jobid. stop %jobid . . . Stops the execution of a background job(s). suspend Stops the execution of the current shell (but not if it is the login shell). wait [%jobid ...] wait builtin accepts a job identifier. If %jobid is omitted, wait behaves as described above under Special Commands. Restricted Shell (/usr/lib/rsh) Only /usr/lib/rsh is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell. The actions of /usr/lib/rsh are identical to those of sh, except that the following are disallowed: + changing directory (see cd(1)) + setting the value of $PATH + specifying path or command names containing / + redirecting output (> and >>) The restrictions above are enforced after .profile is interpreted. A restricted shell can be invoked in one of the following ways: (1) rsh is the filename part of the last entry in the /etc/passwd file (see passwd(4)); (2) the environment variable SHELL exists and rsh is the filename part of its value; (3) the shell is invoked and rsh is the filename part of argument 0; (4) the shell is invoke with the -r option. When a command to be executed is found to be a shell procedure, /usr/lib/rsh invokes sh to execute it. Thus, it is possible to provide to the end-user shell procedures that have access to the full power of the standard shell, while imposing a limited menu of commands; this scheme assumes that the end-user does not have write and execute permissions in the same directory. The net effect of these rules is that the writer of the .profile (see profile(4)) has complete control over user actions by performing guaranteed setup actions and leaving the user in an appropriate directory (probably not the login directory). The system administrator often sets up a directory of commands (that is, /usr/rbin) that can be safely invoked by a restricted shell. IRIX provides a restricted editor, red(1). EXIT STATUS Errors detected by the shell, such as syntax errors, cause the shell to return a nonzero exit status. If the shell is being used noninteractively execution of the shell file is abandoned. Otherwise, the shell returns the exit status of the last command executed (see also the exit command above). jsh Only If the shell is invoked as jsh and an attempt is made to exit the shell while there are stopped jobs, the shell issues one warning: UX:jsh:WARNING:there are stopped jobs This is the only message. If another exit attempt is made and there are still stopped jobs, they are sent a SIGHUP signal from the kernel and the shell is exited. FILES /etc/profile $HOME/.profile /tmp/sh* /dev/null SEE ALSO cd(1), echo(1), env(1), getopts(1), intro(1), login(1), newgrp(1), pwd(1), systune(1m), test(1), umask(1), wait(1), xargs(1), dup(2), exec(2), fork(2), getrlimit(2), pipe(2), signal(2), ulimit(2), profile(4). CAVEATS Positional parameters have a range of 0 to 9. Attempting to use the positional parameter $10 gives the contents of $1 followed by a 0, which is probably not the desired result. Words used for filenames in input/output redirection are not interpreted for filename generation (see Filename Generation, above). For example, cat file1 >a* creates a file with the name a*. Because commands in pipelines are run as separate processes, variables set in a pipeline have no effect on the parent shell. If you get the error message "cannot fork, too many processes", try using the wait(1) command to clean up your background processes. If this doesn't help, the system process table is probably full or you have too many active foreground processes. (There is a limit to the number of process ids associated with your login, and to the number the system can keep track of.) For compatibility with the POSIX builtin executables linked to /sbin/builtin_exec, the Korn shell parameter expansion ${parameter##pattern} has been implemented only for the specific pattern '*/' to emulate basename. This allows the Bourne shell builtins to work correctly when called with fullpaths e.g. /sbin/jobs. NOTES Sometimes, particularly when using wildcards, the shell will fail to execute a command, and complain with the message Arg list or environment too large This can often be avoided by using multiple commands, the xargs(1) command, or by increasing the ncargs kernel parameter with the systune(1m) command. BUGS Only the last process in a pipeline can be waited for. If a command is executed, and a command with the same name is installed in a directory in the search path before the directory where the original command was found, the shell continues to exec the original command. Use the hash command to correct this situation. Prior to IRIX Release 5.0, the rsh command invoked the restricted shell. This restricted shell command is /usr/lib/rsh and it can be executed by using the full pathname. Beginning with IRIX Release 5.0, the rsh command is the remote shell. See rsh_bsd(1C). Page 19