xargs(1) User Commands xargs(1)NAMExargs - construct argument lists and invoke utility
SYNOPSIS
/usr/bin/xargs [-t] [-p] [ -e [eofstr]] [-E eofstr] [-I replstr] [ -i
[replstr]] [-L number] [ -l [number]] [ -n number [-x]] [-s size] [
utility [ argument...]]
/usr/xpg6/bin/xargs [-t] [-p] [ -e [eofstr]] [-E eofstr] [-I replstr] [
-i [replstr]] [-L number] [ -l [number]] [ -n number [-x]] [-s size] [
utility [ argument...]]
DESCRIPTION
The xargs utility constructs a command line consisting of the utility
and argument operands specified followed by as many arguments read in
sequence from standard input as will fit in length and number con‐
straints specified by the options. The xargs utility then invokes the
constructed command line and waits for its completion. This sequence is
repeated until an end-of-file condition is detected on standard input
or an invocation of a constructed command line returns an exit status
of 255.
Arguments in the standard input must be separated by unquoted blank
characters, or unescaped blank characters or newline characters. A
string of zero or more non-double-quote (") and non-newline characters
can be quoted by enclosing them in double-quotes. A string of zero or
more non-apostrophe (') and non-newline characters can be quoted by
enclosing them in apostrophes. Any unquoted character can be escaped by
preceding it with a backslash (\). The utility will be executed one or
more times until the end-of-file is reached. The results are unspeci‐
fied if the utility named by utility attempts to read from its standard
input.
The generated command line length will be the sum of the size in bytes
of the utility name and each argument treated as strings, including a
null byte terminator for each of these strings. The xargs utility will
limit the command line length such that when the command line is
invoked, the combined argument and environment lists will not exceed
{ARG_MAX}−2048 bytes. Within this constraint, if neither the -n nor the
-s option is specified, the default command line length will be at
least {LINE_MAX}.
OPTIONS
The following options are supported:
-e[eofstr] Uses eofstr as the logical end-of-file string. Under‐
score (_) is assumed for the logical EOF string if nei‐
ther -e nor -E is used. When the eofstr option-argument
is omitted, the logical EOF string capability is dis‐
abled and underscores are taken literally. The xargs
utility reads standard input until either end-of-file
or the logical EOF string is encountered.
-E eofstr In /usr/bin/args:
Specifies a logical end-of-file string to replace the
default underscore. The xargs utility reads standard
input until either end-of-file or the logical EOF
string is encountered. The eofstr cannot be a null
string.
In /usr/xpg6/bin/args:
Specifies a logical end-of-file string to replace the
default underscore. The xargs utility reads standard
input until either end-of-file or the logical EOF
string is encountered. When eofstr is a null string,
the logical end-of-file string capability is disabled
and underscore characters are taken literally.
-I replstr Insert mode. utility is executed for each line from
standard input, taking the entire line as a single
argument, inserting it in argument s for each occur‐
rence of replstr. A maximum of five arguments in argu‐
ments can each contain one or more instances of
replstr. Any blank characters at the beginning of each
line are ignored. Constructed arguments cannot grow
larger than 255 bytes. Option -x is forced on. The -I
and -i options are mutually exclusive; the last one
specified takes effect.
-i[replstr] This option is equivalent to -I replstr. The string {}
is assumed for replstr if the option-argument is omit‐
ted.
-L number The utility is executed for each non-empty number lines
of arguments from standard input. The last invocation
of utility will be with fewer lines of arguments if
fewer than number remain. A line is considered to end
with the first newline character unless the last char‐
acter of the line is a blank character; a trailing
blank character signals continuation to the next non-
empty line, inclusive. The -L, -l, and -n options are
mutually exclusive; the last one specified takes
effect.
-l[number] (The letter ell.) This option is equivalent to -L num‐
ber. If number is omitted, 1 is assumed. Option -x is
forced on.
-n number Invokes utility using as many standard input arguments
as possible, up to number (a positive decimal integer)
arguments maximum. Fewer arguments will be used if:
· The command line length accumulated exceeds the
size specified by the -s option (or {LINE_MAX} if
there is no -s option), or
· The last iteration has fewer than number, but not
zero, operands remaining.
-p Prompt mode. The user is asked whether to execute
utility at each invocation. Trace mode (-t) is turned
on to write the command instance to be executed, fol‐
lowed by a prompt to standard error. An affirmative
response (specific to the user's locale) read from
/dev/tty will execute the command; otherwise, that par‐
ticular invocation of utility is skipped.
-s size Invokes utility using as many standard input arguments
as possible yielding a command line length less than
size (a positive decimal integer) bytes. Fewer argu‐
ments will be used if:
· The total number of arguments exceeds that speci‐
fied by the -n option, or
· The total number of lines exceeds that specified
by the -L option, or
· End of file is encountered on standard input
before size bytes are accumulated.
Values of size up to at least {LINE_MAX} bytes are sup‐
ported, provided that the constraints specified in
DESCRIPTION are met. It is not considered an error if a
value larger than that supported by the implementation
or exceeding the constraints specified in DESCRIPTION
is given. xargs will use the largest value it supports
within the constraints.
-t Enables trace mode. Each generated command line will be writ‐
ten to standard error just prior to invocation.
-x Terminates if a command line containing number arguments (see
the -n option above) or number lines (see the -L option above)
will not fit in the implied or specified size (see the -s
option above).
OPERANDS
The following operands are supported:
utility The name of the utility to be invoked, found by search
path using the PATH environment variable. (ee envi‐
ron(5).) If utility is omitted, the default is the
echo(1) utility. If the utility operand names any of
the special built-in utilities in shell_builtins(1),
the results are undefined.
argument An initial option or operand for the invocation of
utility.
USAGE
The 255 exit status allows a utility being used by xargs to tell xargs
to terminate if it knows no further invocations using the current data
stream will succeed. Thus, utility should explicitly exit with an
appropriate value to avoid accidentally returning with 255.
Notice that input is parsed as lines. Blank characters separate argu‐
ments. If xargs is used to bundle output of commands like find dir
-print or ls into commands to be executed, unexpected results are
likely if any filenames contain any blank characters or newline charac‐
ters. This can be fixed by using find to call a script that converts
each file found into a quoted string that is then piped to xargs.
Notice that the quoting rules used by xargs are not the same as in the
shell. They were not made consistent here because existing applications
depend on the current rules and the shell syntax is not fully compati‐
ble with it. An easy rule that can be used to transform any string into
a quoted form that xargs will interpret correctly is to precede each
character in the string with a backslash (\).
On implementations with a large value for {ARG_MAX}, xargs may produce
command lines longer than {LINE_MAX}. For invocation of utilities, this
is not a problem. If xargs is being used to create a text file, users
should explicitly set the maximum command line length with the -s
option.
The xargs utility returns exit status 127 if an error occurs so that
applications can distinguish "failure to find a utility" from "invoked
utility exited with an error indication." The value 127 was chosen
because it is not commonly used for other meanings; most utilities use
small values for "normal error conditions" and the values above 128 can
be confused with termination due to receipt of a signal. The value 126
was chosen in a similar manner to indicate that the utility could be
found, but not invoked.
EXAMPLES
Example 1: Using the xargs command
The following will move all files from directory $1 to directory $2,
and echo each move command just before doing it:
example% ls $1 | xargs-I {} -t mv $1/{} $2/{}
The following command will combine the output of the parenthesised com‐
mands onto one line, which is then written to the end of file log:
example% (logname; date; printf "%s\n" "$0 $*") | xargs >>log
The following command will invoke diff with successive pairs of argu‐
ments originally typed as command line arguments (assuming there are no
embedded blank characters in the elements of the original argument
list):
example% printf "%s\n" "$*" | xargs-n 2 -x diff
The user is asked which files in the current directory are to be
archived. The files are archived into arch ; a, one at a time, or b,
many at a time:
example% ls | xargs-p -L 1 ar -r arch
ls | xargs-p -L 1 | xargs ar -r arch
The following will execute with successive pairs of arguments origi‐
nally typed as command line arguments:
example% echo $* | xargs-n 2 diff
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables
that affect the execution of xargs: LANG, LC_ALL, LC_COLLATE, LC_CTYPE,
LC_MESSAGES, and NLSPATH.
PATH Determine the location of utility.
EXIT STATUS
The following exit values are returned:
0 All invocations of utility returned exit status 0.
1−125 A command line meeting the specified requirements could
not be assembled, one or more of the invocations of
utility returned a non-zero exit status, or some other
error occurred.
126 The utility specified by utility was found but could
not be invoked.
127 The utility specified by utility could not be found.
If a command line meeting the specified requirements cannot be assem‐
bled, the utility cannot be invoked, an invocation of the utility is
terminated by a signal, or an invocation of the utility exits with exit
status 255, the xargs utility will write a diagnostic message and exit
without processing any remaining input.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWcsu │
├─────────────────────────────┼─────────────────────────────┤
│CSI │Enabled │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOecho(1), shell_builtins(1), attributes(5), environ(5), standards(5)SunOS 5.10 3 Sep 2003 xargs(1)
