xargs(1) DG/UX R4.11MU05 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 flags you specify determine the number of arguments read for each
command invocation and how they are combined.
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. Then, command is executed with the accumulated
arguments. This process is repeated until there are no more
arguments. 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
argument and inserting it in initial-arguments for
each occurrence of replstr. A maximum of five
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, or xargs terminates
execution.
-t Trace mode: The command and each constructed argument
list are echoed to file descriptor 2 just before 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 none 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,
plus the count of characters in the command name.
-eeofstr Eofstr is taken as the logical end-of-file string.
Underscore (_) 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
(underscore is taken literally). Xargs reads standard
input until either end-of-file or the logical EOF
string is encountered.
Xargs will terminate if it receives a return code of -1 from command,
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
In the Bourne shell 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/{}
In the Bourne shell 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. Xargs archives them into arch one at a time (1.), or many
at a time (2.).
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
DIAGNOSTICS
Self-explanatory.
SEE ALSO
sh(1).
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