XARGS(1) BSD General Commands Manual XARGS(1)
xargs -- construct argument list(s) and execute utility
xargs [-0oprt] [-E eofstr] [-I replstr [-R replacements] [-S replsize]] [-J replstr] [-L number] [-n number [-x]] [-P maxprocs] [-s size]
[utility [argument ...]]
The xargs utility reads space, tab, newline and end-of-file delimited strings from the standard input and executes utility with the strings
Any arguments specified on the command line are given to utility upon each invocation, followed by some number of the arguments read from the
standard input of xargs. This is repeated until standard input is exhausted.
Spaces, tabs and newlines may be embedded in arguments using single (`` ' '') or double (``"'') quotes or backslashes (``''). Single quotes
escape all non-single quote characters, excluding newlines, up to the matching single quote. Double quotes escape all non-double quote char-
acters, excluding newlines, up to the matching double quote. Any single character, including newlines, may be escaped by a backslash.
The options are as follows:
-0 Change xargs to expect NUL (`` '') characters as separators, instead of spaces and newlines. This is expected to be used in concert
with the -print0 function in find(1).
Use eofstr as a logical EOF marker.
Execute utility for each input line, replacing one or more occurrences of replstr in up to replacements (or 5 if no -R flag is speci-
fied) arguments to utility with the entire line of input. The resulting arguments, after replacement is done, will not be allowed to
grow beyond replsize (or 255 if no -S flag is specified) bytes; this is implemented by concatenating as much of the argument contain-
ing replstr as possible, to the constructed arguments to utility, up to replsize bytes. The size limit does not apply to arguments
to utility which do not contain replstr, and furthermore, no replacement will be done on utility itself. Implies -x.
If this option is specified, xargs will use the data read from standard input to replace the first occurrence of replstr instead of
appending that data after all other arguments. This option will not affect how many arguments will be read from input (-n), or the
size of the command(s) xargs will generate (-s). The option just moves where those arguments will be placed in the command(s) that
are executed. The replstr must show up as a distinct argument to xargs. It will not be recognized if, for instance, it is in the
middle of a quoted string. Furthermore, only the first occurrence of the replstr will be replaced. For example, the following com-
mand will copy the list of files and directories which start with an uppercase letter in the current directory to destdir:
/bin/ls -1d [A-Z]* | xargs -J % cp -Rp % destdir
Call utility for every number lines read. If EOF is reached and fewer lines have been read than number then utility will be called
with the available lines.
Set the maximum number of arguments taken from standard input for each invocation of utility. An invocation of utility will use less
than number standard input arguments if the number of bytes accumulated (see the -s option) exceeds the specified size or there are
fewer than number arguments remaining for the last invocation of utility. The current default value for number is 5000.
-o Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive
Parallel mode: run at most maxprocs invocations of utility at once.
-p Echo each command to be executed and ask the user whether it should be executed. An affirmative response, 'y' in the POSIX locale,
causes the command to be executed, any other response causes it to be skipped. No commands are executed if the process is not
attached to a terminal.
-r Compatibility with GNU xargs. The GNU version of xargs runs the utility argument at least once, even if xargs input is empty, and it
supports a -r option to inhibit this behavior. The FreeBSD version of xargs does not run the utility argument on empty input, but it
supports the -r option for command-line compatibility with GNU xargs, but the -r option does nothing in the FreeBSD version of xargs.
Specify the maximum number of arguments that -I will do replacement in. If replacements is negative, the number of arguments in
which to replace is unbounded.
Specify the amount of space (in bytes) that -I can use for replacements. The default for replsize is 255.
Set the maximum number of bytes for the command line length provided to utility. The sum of the length of the utility name, the
arguments passed to utility (including NULL terminators) and the current environment will be less than or equal to this number. The
current default value for size is ARG_MAX - 4096.
-t Echo the command to be executed to standard error immediately before it is executed.
-x Force xargs to terminate immediately if a command line containing number arguments will not fit in the specified (or default) command
If utility is omitted, echo(1) is used.
Undefined behavior may occur if utility reads from the standard input.
If a command line cannot be assembled, or cannot be invoked, or if an invocation of utility is terminated by a signal, or an invocation of
utility exits with a value of 255, the xargs utility stops processing input and exits after all invocations of utility finish processing.
The xargs utility exits with a value of 0 if no error occurs. If utility cannot be found, xargs exits with a value of 127, otherwise if
utility cannot be executed, xargs exits with a value of 126. If any other error occurs, xargs exits with a value of 1.
echo(1), find(1), execvp(3)
The xargs utility is expected to be IEEE Std 1003.2 (``POSIX.2'') compliant. The -J, -o, -P, -R and -S options are non-standard FreeBSD
extensions which may not be available on other operating systems.
The xargs utility appeared in PWB UNIX.
If utility attempts to invoke another command such that the number of arguments or the size of the environment is increased, it risks
execvp(3) failing with E2BIG.
The xargs utility does not take multibyte characters into account when performing string comparisons for the -I and -J options, which may
lead to incorrect results in some locales.
March 16, 2012 BSD