Translations by Wenbin Lv

time [-p] pipeline

case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esac

job_spec [&]

Exit for, while, or until loops. Exit a FOR, WHILE or UNTIL loop. If N is specified, break N enclosing loops. Exit Status: The exit status is 0 unless N is not greater than or equal to 1.

Resume for, while, or until loops. Resumes the next iteration of the enclosing FOR, WHILE or UNTIL loop. If N is specified, resumes the Nth enclosing loop. Exit Status: The exit status is 0 unless N is not greater than or equal to 1.

Return the context of the current subroutine call. Without EXPR, returns "$line $filename". With EXPR, returns "$line $subroutine $filename"; this extra information can be used to provide a stack trace. The value of EXPR indicates how many call frames to go back before the current one; the top frame is frame 0. Exit Status: Returns 0 unless the shell is not executing a shell function or EXPR is invalid.

Return a successful result. Exit Status: Always succeeds.

Write arguments to the standard output. Display the ARGs on the standard output followed by a newline. Options: -n do not append a newline Exit Status: Returns success unless a write error occurs.

Enable and disable shell builtins. Enables and disables builtin shell commands. Disabling allows you to execute a disk command which has the same name as a shell builtin without using a full pathname. Options: -a print a list of builtins showing whether or not each is enabled -n disable each NAME or display a list of disabled builtins -p print the list of builtins in a reusable format -s print only the names of Posix `special' builtins Options controlling dynamic loading: -f Load builtin NAME from shared object FILENAME -d Remove a builtin loaded with -f Without options, each NAME is enabled. To use the `test' found in $PATH instead of the shell builtin version, type `enable -n test'. Exit Status: Returns success unless NAME is not a shell builtin or an error occurs.

Execute arguments as a shell command. Combine ARGs into a single string, use the result as input to the shell, and execute the resulting commands. Exit Status: Returns exit status of command or success if command is null.

Exit the shell. Exits the shell with a status of N. If N is omitted, the exit status is that of the last command executed.

Exit a login shell. Exits a login shell with exit status N. Returns an error if not executed in a login shell.

Display or execute commands from the history list. fc is used to list or edit and re-execute commands from the history list. FIRST and LAST can be numbers specifying the range, or FIRST can be a string, which means the most recent command beginning with that string. Options: -e ENAME select which editor to use. Default is FCEDIT, then EDITOR, then vi -l list lines instead of editing -n omit line numbers when listing -r reverse the order of the lines (newest listed first) With the `fc -s [pat=rep ...] [command]' format, COMMAND is re-executed after the substitution OLD=NEW is performed. A useful alias to use with this is r='fc -s', so that typing `r cc' runs the last command beginning with `cc' and typing `r' re-executes the last command. Exit Status: Returns success or status of executed command; non-zero if an error occurs.

Move job to the foreground. Place the job identified by JOB_SPEC in the foreground, making it the current job. If JOB_SPEC is not present, the shell's notion of the current job is used. Exit Status: Status of command placed in foreground, or failure if an error occurs.

Move jobs to the background. Place the jobs identified by each JOB_SPEC in the background, as if they had been started with `&'. If JOB_SPEC is not present, the shell's notion of the current job is used. Exit Status: Returns success unless job control is not enabled or an error occurs.

Evaluate arithmetic expressions. Evaluate each ARG as an arithmetic expression. Evaluation is done in fixed-width integers with no check for overflow, though division by 0 is trapped and flagged as an error. The following list of operators is grouped into levels of equal-precedence operators. The levels are listed in order of decreasing precedence. id++, id-- variable post-increment, post-decrement ++id, --id variable pre-increment, pre-decrement -, + unary minus, plus !, ~ logical and bitwise negation ** exponentiation *, /, % multiplication, division, remainder +, - addition, subtraction <<, >> left and right bitwise shifts <=, >=, <, > comparison ==, != equality, inequality & bitwise AND ^ bitwise XOR | bitwise OR && logical AND || logical OR expr ? expr : expr conditional operator =, *=, /=, %=, +=, -=, <<=, >>=, &=, ^=, |= assignment Shell variables are allowed as operands. The name of the variable is replaced by its value (coerced to a fixed-width integer) within an expression. The variable need not have its integer attribute turned on to be used in an expression. Operators are evaluated in order of precedence. Sub-expressions in parentheses are evaluated first and may override the precedence rules above. Exit Status: If the last ARG evaluates to 0, let returns 1; let returns 0 otherwise.

Return from a shell function. Causes a function or sourced script to exit with the return value specified by N. If N is omitted, the return status is that of the last command executed within the function or script. Exit Status: Returns N, or failure if the shell is not executing a function or script.

Set export attribute for shell variables. Marks each NAME for automatic export to the environment of subsequently executed commands. If VALUE is supplied, assign VALUE before exporting. Options: -f refer to shell functions -n remove the export property from each NAME -p display a list of all exported variables and functions 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. 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 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.

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.

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.

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.

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.

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