XARGS(1) SysV 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 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 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).