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xargs(1)
xargs(1) User Commands xargs(1)
NAME
xargs - construct argument lists and invoke utility
SYNOPSIS
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 fit in length and number constraints
specified by the options. The xargs utility then invokes the con‐
structed 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 are executed one or more
times until the end-of-file is reached. The results are unspecified if
the utility named by utility attempts to read from its standard input.
The generated command line length is 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 limits the
command line length such that when the command line is invoked, the
combined argument and environment lists can not exceed {ARG_MAX}−2048
bytes. Within this constraint, if neither the -n nor the -s option is
specified, the default command line length is at least {LINE_MAX}.
OPTIONS
The following options are supported:
-0
Input items are terminated by a null character instead of by white
space or a NEWLINE, and the quotes and backslash are not special,
that is, every character is taken literally. The end of file string
is also disabled and is treated like any other argument. This is
useful when input items might contain white space, quote marks, or
backslashes. The find -print0 option produces input suitable for
this mode.
-e[eofstr]
Uses eofstr as the logical end-of-file string. Underscore (_) is
assumed for the logical EOF string if neither -e nor -E is used.
When the eofstr option-argument is omitted, the logical EOF string
capability is disabled 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
Specifies a logical end-of-file string to replace the default
underscore. xargs 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 argu‐
ment s for each occurrence of replstr. A maximum of five arguments
in arguments can each contain one or more instances of replstr. Any
blank characters at the beginning of each line are ignored. Con‐
structed 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 omitted.
-L number
The utility is executed for each non-empty number lines of argu‐
ments from standard input. The last invocation of utility is with
fewer lines of arguments if fewer than number remain. A line is
considered to end with the first newline character unless the last
character of the line is a blank character; a trailing blank char‐
acter 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 number. If num‐
ber 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 are used if:
o The command line length accumulated exceeds the size
specified by the -s option (or {LINE_MAX} if there is no
-s option), or
o 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, followed by a prompt to standard error. An
affirmative response (specific to the user's locale) read from
/dev/tty executes the command; otherwise, that particular invoca‐
tion 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 arguments are used if:
o The total number of arguments exceeds that specified by
the -n option, or
o The total number of lines exceeds that specified by the
-L option, or
o End of file is encountered on standard input before size
bytes are accumulated.
Values of size up to at least {LINE_MAX} bytes are supported, pro‐
vided 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 specified. xargs uses the largest value it supports
within the constraints.
-t
Enables trace mode. Each generated command line is written to stan‐
dard 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) does 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 environ(7).) If
utility is omitted, the default is the echo(1) utility. If
the utility operand names any of the special built-in util‐
ities 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 succeeds. Thus, utility should explicitly exit with an appropri‐
ate 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 interprets correctly is to precede each char‐
acter in the string with a backslash (\).
On implementations with a large value for {ARG_MAX}, xargs can 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 example moves 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 combines the output of the parenthesised commands
onto one line, which is then written to the end of file log:
example% (logname; date; printf "%s\n" "$0 $*") | xargs >>log
The following command invokes diff with successive pairs of arguments
originally typed as command line arguments (assuming there are no
embedded blank characters in the elements of the original argument
list):
example% printf "%s\n" "$*" | 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 executes with successive pairs of arguments originally
typed as command line arguments:
example% echo $* | xargs -n 2 diff
ENVIRONMENT VARIABLES
See environ(7) 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.
Affirmative responses are processed using the extended regular expres‐
sion defined for the yesexpr keyword in the LC_MESSAGES category of the
user's locale. The locale specified in the LC_COLLATE category defines
the behavior of ranges, equivalence classes, and multi-character col‐
lating elements used in the expression defined for yesexpr. The locale
specified in LC_CTYPE determines the locale for interpretation of
sequences of bytes of text data a characters, the behavior of character
classes used in the expression defined for the yesexpr. See locale(7).
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 writes a diagnostic message and exit
without processing any remaining input.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ Availabilitysystem/core-os _ CSIEnabled _ Interface
StabilityCommitted _ StandardSee standards(7).
SEE ALSO
echo(1), shell_builtins(1), attributes(7), environ(7), standards(7)
Oracle Solaris 11.4 2 Nov 2010 xargs(1)