xargs(1) xargs(1)
NAME [Toc] [Back]
xargs - construct argument list(s) and execute command
SYNOPSIS [Toc] [Back]
xargs [options] [command [initial-arguments]]
DESCRIPTION [Toc] [Back]
xargs combines the fixed initial-arguments with arguments read from
standard input to execute the specified command one or more times.
The number of arguments read for each command invocation and the
manner in which they are combined are determined by the options
specified.
command, which can be a shell file, is searched for, using the $PATH
environment variable. If command is omitted, /usr/bin/echo is used.
Arguments read in from standard input are defined to be contiguous
strings of characters delimited by one or more blanks, tabs, or newlines;
empty lines are always discarded. Spaces and tabs can be
embedded as part of an argument if escaped or quoted. Characters
enclosed in quotes (single or double) are taken literally, and the
delimiting quotes are removed. Outside of quoted strings, a backslash
(\) escapes the next character.
The amount of memory available for the execution of command is limited
by the system parameter ARG_MAX. By default, the size of the argument
list is limited to LINE_MAX bytes. See limits(5) and sysconf(2) for a
description of these system parameters and how their values can be
determined. To increase the available argument list space, use the -s
option.
Each argument list is constructed starting with the initial-arguments,
followed by some number of arguments read from standard input
(exception: see -i or -I option). The -i, -I, -l, -L, and -n options
determine how arguments are selected for each command invocation.
When none of these options is specified, the initial-arguments are
followed by arguments read continuously from standard input until an
internal buffer is full, then command is executed with the accumulated
args. This process is repeated until there are no more args. When
there are option conflicts (such as -l or -L versus -n), the last
option has precedence. option values are:
-L number command is executed for each non-empty number
lines of arguments from standard input. The last
invocation of command will be with fewer lines of
arguments if fewer than number remain. A line is
considered to end with the first new-line unless
the last character of the line is a blank or a
tab; a trailing blank/tab signals continuation
through the next non-empty line. The -L, -l, and
-n options are mutually exclusive. The last one
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specified takes effect.
-l[ number ] This option is equivalent to the -L option. 1 is
assumed if number is omitted or is given as the
empty string ( "" ). Option -x is forced.
-I replstr Insert mode: command is executed for each line
from standard input, taking the entire line as a
single arg, inserting it in initial-arguments for
each occurrence of replstr. A maximum of 5
arguments in initial-arguments can each contain
one or more instances of replstr. Blanks and tabs
at the beginning of each line are discarded.
Constructed arguments must not grow larger than
255 bytes, and option -x is also forced. The -I
and -i options are mutually exclusive. The last
one specified takes effect.
-i[ repstr ] This option is equivalent to the -I option. {} is
assumed if replstr is omitted or is given as the
empty string ( "" ).
-n number Execute command using as many standard input
arguments as possible, up to number arguments
maximum. Fewer arguments are used if their total
size is greater than size bytes, and for the last
invocation if there are fewer than number
arguments remaining. If option -x is also coded,
each number arguments must fit in the size
limitation or xargs terminates execution.
-s size The maximum total size of each argument list is
set to size bytes; size must be a positive integer
less than LINE_MAX (see limits(5), sysconf(2)).
If -s is not coded, LINE_MAX is taken as the
default. Note that the bytes count for size
includes one extra bytes for each argument and the
count of bytes in the command name.
-t Trace mode: The command and each constructed
argument list are echoed to standard error just
prior to their execution.
-p Prompt mode: The user is asked whether to execute
command prior to each invocation. Trace mode (-t)
is turned on to print the command instance to be
executed, followed by a ?... prompt. An
affirmative reply (by default, an affirmative
reply is y optionally followed by anything)
executes the command; anything else, including
pressing Return, skips that particular invocation
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of command.
-x Causes xargs to terminate if any argument list
would be greater than size bytes. -x is forced by
the options -i, -I, -l, and -L. When none of the
options -i, -I, -l, -L, or -n is coded, the total
length of all arguments must be within the size
limit.
-e[ eofstr ] eofstr is taken as the logical end-of-file string.
Underscore (_) is assumed for the logical EOF
string if neither -e nor -E is used. The value -e
with eofstr given as the empty string ( "" ) turns
off the logical EOF string capability (underscore
is taken literally). xargs reads standard input
until either end-of-file or the logical EOF string
is encountered.
-E eofstr Specify a logical end-of-file string to replace
the default underscore (_) character. Equivalent
to the -e option above.
xargs terminates if it receives a return code of -1 from command or if
it cannot execute command. When command is a shell program, it should
explicitly exit (see sh(1)) with an appropriate value to avoid
accidentally returning with -1.
RETURN VALUE [Toc] [Back]
xargs exits with one of the following values:
0 All invocations of command completed successfully.
1-125
One or more invocations of command did not complete
successfully.
126 The command specified was found but could not be invoked.
127 The command specified could not be found.
EXTERNAL INFLUENCES [Toc] [Back]
Environment Variables
LC_CTYPE determines the space characters and the interpretation of
text as single- and/or multi-byte characters.
LC_MESSAGES determines the language in which messages are displayed,
and the local language equivalent of an affirmative reply when the -p
prompt option is specified.
If LC_CTYPE or LC_MESSAGES is not specified in the environment or is
set to the empty string, the value of LANG is used as a default for
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each unspecified or empty variable. If LANG is not specified or is
set to the empty string, a default of "C" (see lang(5)) is used
instead of LANG.
If any internationalization variable contains an invalid setting,
xargs behaves as if all internationalization variables are set to "C".
See environ(5).
International Code Set Support [Toc] [Back]
Single- and multi-byte character code sets are supported.
EXAMPLES [Toc] [Back]
Move all files from directory $1 to directory $2, and echo each move
command just before doing it:
ls $1 | xargs -i -t mv $1/{} $2/{}
Combine the output of the parenthesized commands onto one line, then
echo to the end of file log:
(logname; date; echo $0 $*) | xargs >>log
Ask the user which files in the current directory are to be archived
then archive them into arch one at a time:
ls | xargs -p -l ar r arch
or many at a time:
ls | xargs -p -l | xargs ar r arch
Execute diff (see diff(1)) with successive pairs of arguments
originally typed as shell arguments:
echo $* | xargs -n2 diff
SEE ALSO [Toc] [Back]
sh(1).
STANDARDS CONFORMANCE [Toc] [Back]
xargs: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2
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