xargs - construct argument list(s) and execute utility
xargs [-0opt] [-E eofstr] [-I replstr [-R replacements]] [-J
replstr]
[-L number] [-n number [-x]] [-P maxjobs] [-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 standard
input. The utility is repeatedly executed 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 characters, 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).
-E eofstr
Use eofstr as a logical EOF marker.
-I replstr
Execute utility for each input line, replacing one
or more occurrences
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 concatenating
as much of the argument containing replstr as
possible, 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 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 command 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
-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 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
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
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 replacements
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.
-s size
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 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 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
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 input)
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'') compliant.
The -J, -o, -P 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 arguments
or the size of the environment is increased, it
risks execvp(3)
failing with E2BIG.
OpenBSD 3.6 May 7, 2001
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