Translations by pan93412

Mark shell variables as unchangeable. Mark each NAME as read-only; the values of these NAMEs may not be changed by subsequent assignment. If VALUE is supplied, assign VALUE before marking as read-only. Options: -a refer to indexed array variables -A refer to associative array variables -f refer to shell functions -p display a list of all readonly variables or functions, depending on whether or not the -f option is given An argument of `--' disables further option processing. Exit Status: Returns success unless an invalid option is given or NAME is invalid.

Shift positional parameters. Rename the positional parameters $N+1,$N+2 ... to $1,$2 ... If N is not given, it is assumed to be 1. Exit Status: Returns success unless N is negative or greater than $#.

Execute commands from a file in the current shell. Read and execute commands from FILENAME in the current shell. The entries in $PATH are used to find the directory containing FILENAME. If any ARGUMENTS are supplied, they become the positional parameters when FILENAME is executed. Exit Status: Returns the status of the last command executed in FILENAME; fails if FILENAME cannot be read.

Suspend shell execution. Suspend the execution of this shell until it receives a SIGCONT signal. Unless forced, login shells cannot be suspended. Options: -f force the suspend, even if the shell is a login shell Exit Status: Returns success unless job control is not enabled or an error occurs.

Evaluate conditional expression. Exits with a status of 0 (true) or 1 (false) depending on the evaluation of EXPR. Expressions may be unary or binary. Unary expressions are often used to examine the status of a file. There are string operators and numeric comparison operators as well. The behavior of test depends on the number of arguments. Read the bash manual page for the complete specification. File operators: -a FILE True if file exists. -b FILE True if file is block special. -c FILE True if file is character special. -d FILE True if file is a directory. -e FILE True if file exists. -f FILE True if file exists and is a regular file. -g FILE True if file is set-group-id. -h FILE True if file is a symbolic link. -L FILE True if file is a symbolic link. -k FILE True if file has its `sticky' bit set. -p FILE True if file is a named pipe. -r FILE True if file is readable by you. -s FILE True if file exists and is not empty. -S FILE True if file is a socket. -t FD True if FD is opened on a terminal. -u FILE True if the file is set-user-id. -w FILE True if the file is writable by you. -x FILE True if the file is executable by you. -O FILE True if the file is effectively owned by you. -G FILE True if the file is effectively owned by your group. -N FILE True if the file has been modified since it was last read. FILE1 -nt FILE2 True if file1 is newer than file2 (according to modification date). FILE1 -ot FILE2 True if file1 is older than file2. FILE1 -ef FILE2 True if file1 is a hard link to file2. String operators: -z STRING True if string is empty. -n STRING STRING True if string is not empty. STRING1 = STRING2 True if the strings are equal. STRING1 != STRING2 True if the strings are not equal. STRING1 < STRING2 True if STRING1 sorts before STRING2 lexicographically. STRING1 > STRING2 True if STRING1 sorts after STRING2 lexicographically. Other operators: -o OPTION True if the shell option OPTION is enabled. -v VAR True if the shell variable VAR is set. -R VAR True if the shell variable VAR is set and is a name reference. ! EXPR True if expr is false. EXPR1 -a EXPR2 True if both expr1 AND expr2 are true. EXPR1 -o EXPR2 True if either expr1 OR expr2 is true. arg1 OP arg2 Arithmetic tests. OP is one of -eq, -ne, -lt, -le, -gt, or -ge. Arithmetic binary operators return true if ARG1 is equal, not-equal, less-than, less-than-or-equal, greater-than, or greater-than-or-equal than ARG2. Exit Status: Returns success if EXPR evaluates to true; fails if EXPR evaluates to false or an invalid argument is given.

Evaluate conditional expression. This is a synonym for the "test" builtin, but the last argument must be a literal `]', to match the opening `['.

Display process times. Prints the accumulated user and system times for the shell and all of its child processes. Exit Status: Always succeeds.

Trap signals and other events. Defines and activates handlers to be run when the shell receives signals or other conditions. ARG is a command to be read and executed when the shell receives the signal(s) SIGNAL_SPEC. If ARG is absent (and a single SIGNAL_SPEC is supplied) or `-', each specified signal is reset to its original value. If ARG is the null string each SIGNAL_SPEC is ignored by the shell and by the commands it invokes. If a SIGNAL_SPEC is EXIT (0) ARG is executed on exit from the shell. If a SIGNAL_SPEC is DEBUG, ARG is executed before every simple command. If a SIGNAL_SPEC is RETURN, ARG is executed each time a shell function or a script run by the . or source builtins finishes executing. A SIGNAL_SPEC of ERR means to execute ARG each time a command's failure would cause the shell to exit when the -e option is enabled. If no arguments are supplied, trap prints the list of commands associated with each signal. Options: -l print a list of signal names and their corresponding numbers -p display the trap commands associated with each SIGNAL_SPEC Each SIGNAL_SPEC is either a signal name in <signal.h> or a signal number. Signal names are case insensitive and the SIG prefix is optional. A signal may be sent to the shell with "kill -signal $$". Exit Status: Returns success unless a SIGSPEC is invalid or an invalid option is given.

Display information about command type. For each NAME, indicate how it would be interpreted if used as a command name. Options: -a display all locations containing an executable named NAME; includes aliases, builtins, and functions, if and only if the `-p' option is not also used -f suppress shell function lookup -P force a PATH search for each NAME, even if it is an alias, builtin, or function, and returns the name of the disk file that would be executed -p returns either the name of the disk file that would be executed, or nothing if `type -t NAME' would not return `file' -t output a single word which is one of `alias', `keyword', `function', `builtin', `file' or `', if NAME is an alias, shell reserved word, shell function, shell builtin, disk file, or not found, respectively Arguments: NAME Command name to be interpreted. Exit Status: Returns success if all of the NAMEs are found; fails if any are not found.

Modify shell resource limits. Provides control over the resources available to the shell and processes it creates, on systems that allow such control. Options: -S use the `soft' resource limit -H use the `hard' resource limit -a all current limits are reported -b the socket buffer size -c the maximum size of core files created -d the maximum size of a process's data segment -e the maximum scheduling priority (`nice') -f the maximum size of files written by the shell and its children -i the maximum number of pending signals -k the maximum number of kqueues allocated for this process -l the maximum size a process may lock into memory -m the maximum resident set size -n the maximum number of open file descriptors -p the pipe buffer size -q the maximum number of bytes in POSIX message queues -r the maximum real-time scheduling priority -s the maximum stack size -t the maximum amount of cpu time in seconds -u the maximum number of user processes -v the size of virtual memory -x the maximum number of file locks -P the maximum number of pseudoterminals -R the maximum time a real-time process can run before blocking -T the maximum number of threads Not all options are available on all platforms. If LIMIT is given, it is the new value of the specified resource; the special LIMIT values `soft', `hard', and `unlimited' stand for the current soft limit, the current hard limit, and no limit, respectively. Otherwise, the current value of the specified resource is printed. If no option is given, then -f is assumed. Values are in 1024-byte increments, except for -t, which is in seconds, -p, which is in increments of 512 bytes, and -u, which is an unscaled number of processes. Exit Status: Returns success unless an invalid option is supplied or an error occurs.

Display or set file mode mask. Sets the user file-creation mask to MODE. If MODE is omitted, prints the current value of the mask. If MODE begins with a digit, it is interpreted as an octal number; otherwise it is a symbolic mode string like that accepted by chmod(1). Options: -p if MODE is omitted, output in a form that may be reused as input -S makes the output symbolic; otherwise an octal number is output Exit Status: Returns success unless MODE is invalid or an invalid option is given.

Wait for job completion and return exit status. Waits for each process identified by an ID, which may be a process ID or a job specification, and reports its termination status. If ID is not given, waits for all currently active child processes, and the return status is zero. If ID is a job specification, waits for all processes in that job's pipeline. If the -n option is supplied, waits for a single job from the list of IDs, or, if no IDs are supplied, for the next job to complete and returns its exit status. If the -p option is supplied, the process or job identifier of the job for which the exit status is returned is assigned to the variable VAR named by the option argument. The variable will be unset initially, before any assignment. This is useful only when the -n option is supplied. If the -f option is supplied, and job control is enabled, waits for the specified ID to terminate, instead of waiting for it to change status. Exit Status: Returns the status of the last ID; fails if ID is invalid or an invalid option is given, or if -n is supplied and the shell has no unwaited-for children.

Wait for process completion and return exit status. Waits for each process specified by a PID and reports its termination status. If PID is not given, waits for all currently active child processes, and the return status is zero. PID must be a process ID. Exit Status: Returns the status of the last PID; fails if PID is invalid or an invalid option is given.

Execute commands for each member in a list. The `for' loop executes a sequence of commands for each member in a list of items. If `in WORDS ...;' is not present, then `in "$@"' is assumed. For each element in WORDS, NAME is set to that element, and the COMMANDS are executed. Exit Status: Returns the status of the last command executed.

Arithmetic for loop. Equivalent to (( EXP1 )) while (( EXP2 )); do COMMANDS (( EXP3 )) done EXP1, EXP2, and EXP3 are arithmetic expressions. If any expression is omitted, it behaves as if it evaluates to 1. Exit Status: Returns the status of the last command executed.

Select words from a list and execute commands. The WORDS are expanded, generating a list of words. The set of expanded words is printed on the standard error, each preceded by a number. If `in WORDS' is not present, `in "$@"' is assumed. The PS3 prompt is then displayed and a line read from the standard input. If the line consists of the number corresponding to one of the displayed words, then NAME is set to that word. If the line is empty, WORDS and the prompt are redisplayed. If EOF is read, the command completes. Any other value read causes NAME to be set to null. The line read is saved in the variable REPLY. COMMANDS are executed after each selection until a break command is executed. Exit Status: Returns the status of the last command executed.

Report time consumed by pipeline's execution. Execute PIPELINE and print a summary of the real time, user CPU time, and system CPU time spent executing PIPELINE when it terminates. Options: -p print the timing summary in the portable Posix format The value of the TIMEFORMAT variable is used as the output format. Exit Status: The return status is the return status of PIPELINE.

Execute commands based on pattern matching. Selectively execute COMMANDS based upon WORD matching PATTERN. The `|' is used to separate multiple patterns. Exit Status: Returns the status of the last command executed.

Execute commands based on conditional. The `if COMMANDS' list is executed. If its exit status is zero, then the `then COMMANDS' list is executed. Otherwise, each `elif COMMANDS' list is executed in turn, and if its exit status is zero, the corresponding `then COMMANDS' list is executed and the if command completes. Otherwise, the `else COMMANDS' list is executed, if present. The exit status of the entire construct is the exit status of the last command executed, or zero if no condition tested true. Exit Status: Returns the status of the last command executed.

Execute commands as long as a test succeeds. Expand and execute COMMANDS as long as the final command in the `while' COMMANDS has an exit status of zero. Exit Status: Returns the status of the last command executed.

Execute commands as long as a test does not succeed. Expand and execute COMMANDS as long as the final command in the `until' COMMANDS has an exit status which is not zero. Exit Status: Returns the status of the last command executed.

Create a coprocess named NAME. Execute COMMAND asynchronously, with the standard output and standard input of the command connected via a pipe to file descriptors assigned to indices 0 and 1 of an array variable NAME in the executing shell. The default NAME is "COPROC". Exit Status: The coproc command returns an exit status of 0.

Define shell function. Create a shell function named NAME. When invoked as a simple command, NAME runs COMMANDs in the calling shell's context. When NAME is invoked, the arguments are passed to the function as $1...$n, and the function's name is in $FUNCNAME. Exit Status: Returns success unless NAME is readonly.

Group commands as a unit. Run a set of commands in a group. This is one way to redirect an entire set of commands. Exit Status: Returns the status of the last command executed.

Resume job in foreground. Equivalent to the JOB_SPEC argument to the `fg' command. Resume a stopped or background job. JOB_SPEC can specify either a job name or a job number. Following JOB_SPEC with a `&' places the job in the background, as if the job specification had been supplied as an argument to `bg'. Exit Status: Returns the status of the resumed job.

Evaluate arithmetic expression. The EXPRESSION is evaluated according to the rules for arithmetic evaluation. Equivalent to `let "EXPRESSION"'. Exit Status: Returns 1 if EXPRESSION evaluates to 0; returns 0 otherwise.