Translations by Sergio Pokrovskij

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 -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 -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 a job specification, waits for all processes in that job's pipeline. If the -n option is supplied, waits for the next job to terminate and returns its exit status. Exit Status: Returns the status of the last ID; fails if ID is invalid or an invalid option is given.

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: Returns the exit status of COMMAND.

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.

Execute conditional command. Returns a status of 0 or 1 depending on the evaluation of the conditional expression EXPRESSION. Expressions are composed of the same primaries used by the `test' builtin, and may be combined using the following operators: ( EXPRESSION ) Returns the value of EXPRESSION ! EXPRESSION True if EXPRESSION is false; else false EXPR1 && EXPR2 True if both EXPR1 and EXPR2 are true; else false EXPR1 || EXPR2 True if either EXPR1 or EXPR2 is true; else false When the `==' and `!=' operators are used, the string to the right of the operator is used as a pattern and pattern matching is performed. When the `=~' operator is used, the string to the right of the operator is matched as a regular expression. The && and || operators do not evaluate EXPR2 if EXPR1 is sufficient to determine the expression's value. Exit Status: 0 or 1 depending on value of EXPRESSION.

Common shell variable names and usage. BASH_VERSION Version information for this Bash. CDPATH A colon-separated list of directories to search for directories given as arguments to `cd'. GLOBIGNORE A colon-separated list of patterns describing filenames to be ignored by pathname expansion. HISTFILE The name of the file where your command history is stored. HISTFILESIZE The maximum number of lines this file can contain. HISTSIZE The maximum number of history lines that a running shell can access. HOME The complete pathname to your login directory. HOSTNAME The name of the current host. HOSTTYPE The type of CPU this version of Bash is running under. IGNOREEOF Controls the action of the shell on receipt of an EOF character as the sole input. If set, then the value of it is the number of EOF characters that can be seen in a row on an empty line before the shell will exit (default 10). When unset, EOF signifies the end of input. MACHTYPE A string describing the current system Bash is running on. MAILCHECK How often, in seconds, Bash checks for new mail. MAILPATH A colon-separated list of filenames which Bash checks for new mail. OSTYPE The version of Unix this version of Bash is running on. PATH A colon-separated list of directories to search when looking for commands. PROMPT_COMMAND A command to be executed before the printing of each primary prompt. PS1 The primary prompt string. PS2 The secondary prompt string. PWD The full pathname of the current directory. SHELLOPTS A colon-separated list of enabled shell options. TERM The name of the current terminal type. TIMEFORMAT The output format for timing statistics displayed by the `time' reserved word. auto_resume Non-null means a command word appearing on a line by itself is first looked for in the list of currently stopped jobs. If found there, that job is foregrounded. A value of `exact' means that the command word must exactly match a command in the list of stopped jobs. A value of `substring' means that the command word must match a substring of the job. Any other value means that the command must be a prefix of a stopped job. histchars Characters controlling history expansion and quick substitution. The first character is the history substitution character, usually `!'. The second is the `quick substitution' character, usually `^'. The third is the `history comment' character, usually `#'. HISTIGNORE A colon-separated list of patterns used to decide which commands should be saved on the history list.

Add directories to stack. Adds a directory to the top of the directory stack, or rotates the stack, making the new top of the stack the current working directory. With no arguments, exchanges the top two directories. Options: -n Suppresses the normal change of directory when adding directories to the stack, so only the stack is manipulated. Arguments: +N Rotates the stack so that the Nth directory (counting from the left of the list shown by `dirs', starting with zero) is at the top. -N Rotates the stack so that the Nth directory (counting from the right of the list shown by `dirs', starting with zero) is at the top. dir Adds DIR to the directory stack at the top, making it the new current working directory. The `dirs' builtin displays the directory stack. Exit Status: Returns success unless an invalid argument is supplied or the directory change fails.

Remove directories from stack. Removes entries from the directory stack. With no arguments, removes the top directory from the stack, and changes to the new top directory. Options: -n Suppresses the normal change of directory when removing directories from the stack, so only the stack is manipulated. Arguments: +N Removes the Nth entry counting from the left of the list shown by `dirs', starting with zero. For example: `popd +0' removes the first directory, `popd +1' the second. -N Removes the Nth entry counting from the right of the list shown by `dirs', starting with zero. For example: `popd -0' removes the last directory, `popd -1' the next to last. The `dirs' builtin displays the directory stack. Exit Status: Returns success unless an invalid argument is supplied or the directory change fails.

Display directory stack. Display the list of currently remembered directories. Directories find their way onto the list with the `pushd' command; you can get back up through the list with the `popd' command. Options: -c clear the directory stack by deleting all of the elements -l do not print tilde-prefixed versions of directories relative to your home directory -p print the directory stack with one entry per line -v print the directory stack with one entry per line prefixed with its position in the stack Arguments: +N Displays the Nth entry counting from the left of the list shown by dirs when invoked without options, starting with zero. -N Displays the Nth entry counting from the right of the list shown by dirs when invoked without options, starting with zero. Exit Status: Returns success unless an invalid option is supplied or an error occurs.

Set and unset shell options. Change the setting of each shell option OPTNAME. Without any option arguments, list all shell options with an indication of whether or not each is set. Options: -o restrict OPTNAMEs to those defined for use with `set -o' -p print each shell option with an indication of its status -q suppress output -s enable (set) each OPTNAME -u disable (unset) each OPTNAME Exit Status: Returns success if OPTNAME is enabled; fails if an invalid option is given or OPTNAME is disabled.

Formats and prints ARGUMENTS under control of the FORMAT. Options: -v var assign the output to shell variable VAR rather than display it on the standard output FORMAT is a character string which contains three types of objects: plain characters, which are simply copied to standard output; character escape sequences, which are converted and copied to the standard output; and format specifications, each of which causes printing of the next successive argument. In addition to the standard format specifications described in printf(1), printf interprets: %b expand backslash escape sequences in the corresponding argument %q quote the argument in a way that can be reused as shell input %(fmt)T output the date-time string resulting from using FMT as a format string for strftime(3) The format is re-used as necessary to consume all of the arguments. If there are fewer arguments than the format requires, extra format specifications behave as if a zero value or null string, as appropriate, had been supplied. Exit Status: Returns success unless an invalid option is given or a write or assignment error occurs.

Specify how arguments are to be completed by Readline. For each NAME, specify how arguments are to be completed. If no options are supplied, existing completion specifications are printed in a way that allows them to be reused as input. Options: -p print existing completion specifications in a reusable format -r remove a completion specification for each NAME, or, if no NAMEs are supplied, all completion specifications -D apply the completions and actions as the default for commands without any specific completion defined -E apply the completions and actions to "empty" commands -- completion attempted on a blank line When completion is attempted, the actions are applied in the order the uppercase-letter options are listed above. The -D option takes precedence over -E. Exit Status: Returns success unless an invalid option is supplied or an error occurs.

Display possible completions depending on the options. Intended to be used from within a shell function generating possible completions. If the optional WORD argument is supplied, matches against WORD are generated. Exit Status: Returns success unless an invalid option is supplied or an error occurs.

Modify or display completion options. Modify the completion options for each NAME, or, if no NAMEs are supplied, the completion currently being executed. If no OPTIONs are given, print the completion options for each NAME or the current completion specification. Options: -o option Set completion option OPTION for each NAME -D Change options for the "default" command completion -E Change options for the "empty" command completion Using `+o' instead of `-o' turns off the specified option. Arguments: Each NAME refers to a command for which a completion specification must have previously been defined using the `complete' builtin. If no NAMEs are supplied, compopt must be called by a function currently generating completions, and the options for that currently-executing completion generator are modified. Exit Status: Returns success unless an invalid option is supplied or NAME does not have a completion specification defined.

Read lines from the standard input into an indexed array variable. Read lines from the standard input into the indexed array variable ARRAY, or from file descriptor FD if the -u option is supplied. The variable MAPFILE is the default ARRAY. Options: -n count Copy at most COUNT lines. If COUNT is 0, all lines are copied. -O origin Begin assigning to ARRAY at index ORIGIN. The default index is 0. -s count Discard the first COUNT lines read. -t Remove a trailing newline from each line read. -u fd Read lines from file descriptor FD instead of the standard input. -C callback Evaluate CALLBACK each time QUANTUM lines are read. -c quantum Specify the number of lines read between each call to CALLBACK. Arguments: ARRAY Array variable name to use for file data. If -C is supplied without -c, the default quantum is 5000. When CALLBACK is evaluated, it is supplied the index of the next array element to be assigned and the line to be assigned to that element as additional arguments. If not supplied with an explicit origin, mapfile will clear ARRAY before assigning to it. Exit Status: Returns success unless an invalid option is given or ARRAY is readonly or not an indexed array.

Read lines from a file into an array variable. A synonym for `mapfile'.