XARGS(1) BSD Reference Manual XARGS(1)
xargs - construct argument list(s) and execute utility
xargs [-0oprt] [-E eofstr] [-I replstr [-R replacements]] [-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 the specified utility with
the strings as arguments.
Any arguments specified on the command line are given to the utility upon
each invocation, followed by some number of the arguments read from stan-
dard input. The utility is repeatedly executed one or more times 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 sin-
gle quote. Double quotes escape all non-double quote characters, exclud-
ing newlines, up to the matching double quote. Any single character, in-
cluding newlines, may be escaped by a backslash.
The options are as follows:
-0 Change xargs to expect NUL ('\0') characters as separators, in-
stead of spaces and newlines. This is expected to be used in con-
cert with the -print0 function in find(1).
-E eofstr
Use eofstr as a logical EOF marker.
-I replstr
Execute utility for each input line, replacing one or more oc-
currences of replstr in up to replacements (or 5 if no -R flag is
specified) arguments to utility with the entire line of input.
The resulting arguments, after replacement is done, will not be
allowed to grow beyond 255 bytes; this is implemented by con-
catenating as much of the argument containing replstr as possi-
ble, to the constructed arguments to utility, up to 255 bytes.
The 255 byte 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.
-J replstr
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 effect how many arguments will be read from input (-n),
or the size of the command(s) xargs will generate (-s). The op-
tion just moves where those arguments will be placed in the
command(s) that are executed. The replstr must show up as a dis-
tinct argument to xargs. It will not be recognized if, for in-
stance, it is in the middle of a quoted string. Furthermore, only
the first occurrence of the replstr will be replaced. For exam-
ple, the following command will copy the list of files and direc-
tories which start with an uppercase letter in the current direc-
tory to destdir:
/bin/ls -1d [A-Z]* | xargs -J % cp -rp % destdir
-L number
Call utility for every number of lines read. If EOF is reached
and fewer than number lines have been read then utility will be
called with the available lines.
-n number
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 in-
vocation 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 interac-
tive application.
-P maxprocs
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 lo-
cale, 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 replacements
Specify the maximum number of arguments that -I will do replace-
ment in. If replacements is negative, the number of arguments in
which to replace is unbounded.
-r Do not run the command if there are no arguments. Normally the
command is executed at least once even if there are no arguments.
-s size
Set the maximum number of bytes for the command line length pro-
vided to utility. The sum of the length of the utility name, the
arguments passed to utility (including NUL 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 be-
fore it is executed.
-x Force xargs to terminate immediately if a command line containing
number arguments will not fit in the specified (or default) com-
mand line length.
If no utility is specified, echo(1) is used.
Undefined behavior may occur if utility reads from the standard input.
The xargs utility exits immediately (without processing any further in-
put) if a command line cannot be assembled, utility cannot be invoked, an
invocation of utility is terminated by a signal, or an invocation of
utility exits with a value of 255.
xargs exits with one of the following values:
0 All invocations of utility returned a zero exit status.
123 One or more invocations of utility returned a nonzero exit
status.
124 The utility exited with a 255 exit status.
125 The utility was killed or stopped by a signal.
126 The utility was found but could not be executed.
127 The utility could not be found.
1 Some other error occurred.
echo(1), find(1), execvp(3)
The xargs utility is expected to be IEEE Std 1003.2 ("POSIX.2") compli-
ant. The -J, -o, -P, -R and -r options are non-standard extensions which
may not be available on other operating systems.
The meanings of the 123, 124, and 125 exit values were taken from GNU
xargs.
The xargs command appeared in PWB UNIX.
If utility attempts to invoke another command such that the number of ar-
guments or the size of the environment is increased, it risks execvp(3)
failing with E2BIG.
MirBSD #10-current May 7, 2001 2