XARGS(1) XARGS(1)
NAME
xargs - construct argument list(s) and execute command
SYNOPSIS
xargs [flags] [ command [initial-arguments] ]
DESCRIPTION
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 flags specified.
command, which may be a shell file, is searched for, using
one's $PATH. If command is omitted, /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 new-lines; empty lines are always
discarded. Blanks and tabs may 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 (\) will escape the next character.
Each argument list is constructed starting with the
initial-arguments, followed by some number of arguments read
from standard input (Exception: see -i flag). Flags -i, -l,
and -n determine how arguments are selected for each command
invocation. When none of these flags are coded, the
initial-arguments are followed by arguments read
continuously from standard input until an internal buffer is
full, and then command is executed with the accumulated
args. This process is repeated until there are no more
args. When there are flag conflicts (e.g., -l vs. -n), the
last flag has precedence. Flag values are:
-lnumber 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. If number is
omitted, 1 is assumed. Option -x is
forced.
-ireplstr Insert mode: command is executed for
each line from standard input, taking
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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 may
each contain one or more instances of
replstr. Blanks and tabs at the
beginning of each line are thrown away.
Constructed arguments may not grow
larger than 255 characters, and option
-x is also forced. {} is assumed for
replstr if not specified.
-nnumber Execute command using as many standard
input arguments as possible, up to
number arguments maximum. Fewer
arguments will be used if their total
size is greater than size characters,
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, else xargs terminates
execution.
-t Trace mode: The command and each
constructed argument list are echoed to
file descriptor 2 just prior to their
execution.
-p Prompt mode: The user is asked whether
to execute command each invocation.
Trace mode (-t) is turned on to print
the command instance to be executed,
followed by a ?... prompt. A reply of y
(optionally followed by anything) will
execute the command; anything else,
including just a carriage return, skips
that particular invocation of command.
-x Causes xargs to terminate if any
argument list would be greater than size
characters; -x is forced by the options
-i and -l. When neither of the options
-i, -l, or -n are coded, the total
length of all arguments must be within
the size limit.
-ssize The maximum total size of each argument
list is set to size characters; size
must be a positive integer less than or
equal to 470. If -s is not coded, 470 is
taken as the default. Note that the
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character count for size includes one
extra character for each argument and
the count of characters in the command
name.
-eeofstr eofstr is taken as the logical end-of-
file string. Underbar (_) is assumed
for the logical EOF string if -e is not
coded. The value -e with no eofstr
coded turns off the logical EOF string
capability (underbar is taken
literally). xargs reads standard input
until either end-of-file or the logical
EOF string is encountered.
xargs will terminate if either it receives a return code of
-1 from, 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.
EXAMPLES
The following will 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/{}
The following will combine the output of the parenthesized
commands onto one line, which is then echoed to the end of
file log:
(logname; date; echo $0 $*) | xargs >>log
The user is asked which files in the current directory are
to be archived and archives them into arch (1.) one at a
time, or (2.) many at a time.
1. ls | xargs -p -l ar r arch
2. ls | xargs -p -l | xargs ar r arch
The following will execute diff(1) with successive pairs of
arguments originally typed as shell arguments:
echo $* | xargs -n2 diff
SEE ALSO
sh(1).
ORIGIN
AT&T V.3
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