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Commands Reference, Volume 6
Constructs parameter lists and
runs commands.
xargs [ -p ] [
-t ] [ -e [ EOFString ] ]
[ -E EOFString ] [
-i [ ReplaceString ]
] [ -I ReplaceString ]
[ -l
[ Number ] ] [ -L Number ] [ -n Number [ -x ] ] [ -s Size ]
[ Command [ Argument ... ] ]
Note: Do
not put a blank space between the lowercase flags and the parameter.
The generated command line length
is the sum of the size, in bytes, of the Command and each
Argument treated as strings, including a null byte terminator for
each of these strings. The xargs command limits the command
line length. When the constructed command line runs, the combined
Argument and environment lists can not exceed ARG_MAX
bytes. Within this constraint, if you do not specify the -n
or the -s flags, the default command line length is at least the
value specified by LINE_MAX.
| -e[EOFString]
| Obsolete flag. Use the -E flag.
Uses the EOFString
parameter as the logical EOF string. If you do not specify the
-e or the -E flags, underscore (_) is assumed for the
logical EOF string. If you do not specify the EOFString
parameter, the logical EOF string capability is disabled, and underscores are
taken literally. The xargs command reads from standard input
until either EOF or the specified string is reached.
|
| -E
EOFString
| Specifies a logical EOF string to replace the default
underscore(_ ). The xargs command reads standard input
until either EOF or the specified string is reached.
|
| -i[ReplaceString]
| Obsolete flag. Use the -I (Uppercase i) flag.
If you do not specify the
ReplaceString parameter, the string "{}" is used.
Note: The -I (Uppercase i), and the -i
flags are mutually exclusive; the last flag specified takes
effect.
|
| -I
ReplaceString
| (Uppercase i). Inserts each line of standard input as an argument
for the Command parameter, inserting it in Argument for
each occurrence of ReplaceString. ReplaceStrings
can not be used in more than 5 arguments. Blank characters at the
beginning of each standard input line are ignored. Each
Argument can contain one or more ReplaceStrings, but may
not be larger than 255 bytes. The -I flag also turns on the
-x flag.
Note: The -I (Uppercase i), and the -i
flags are mutually exclusive; the last flag specified takes
effect.
|
| -l[Number]
| (Lowercase L). Obsolete flag. Use the -L
flag.
If you do not specify the
Number parameter, a value of 1 is used. The -l
flag also turns on the -x flag.
Note: The -L, -I (Lowercase L), and
-n flags are mutually exclusive; the last flag specified takes
effect.
|
| -L Number
| Runs the Command parameter with the specified number of
nonempty parameter lines read from standard input. The last invocation
of the Command parameter can have fewer parameter lines if fewer
than the specified Number remain. A line ends with the first
new-line character unless the last character of the line is a space or a
tab. A trailing space indicates a continuation through the next
nonempty line.
Note: The -L, -I (Lowercase L), and
-n flags are mutually exclusive; the last flag specified takes
effect.
|
| -n Number
| Runs the Command parameter using as many standard input
arguments as possible, up to the maximum specified by the Number
parameter. The xargs command uses fewer arguments if:
- If the accumulated command line length exceeds the
bytes specified by the -s Size flag.
- The last iteration has fewer than Number,
but not zero, arguments remaining.
Note: The -L, -I (Lowercase L), and
-n flags are mutually exclusive; the last flag specified takes
effect.
|
| -p
| Asks whether to run the Command parameter. It displays
the constructed command line, followed by a
?... (question mark, ellipsis) prompt.
Enter an affirmative response specific to the locale to run the
Command parameter. Any other response causes the
xargs command to skip that particular invocation of the
parameter. You are asked about each invocation. The
-p flag also turns on the -t flag.
|
| -s Size
| Sets the maximum total size of the constructed Command
line. The Size parameter must be a positive integer.
Fewer arguments are used if:
- The total number of arguments exceeds those specified
by the -n flag.
- The total number of lines exceeds those specified by
the -L or -I (Lowercase L) flags.
- EOF is reached before the number of bytes specified by
the Size parameter are accumulated.
|
| -t
| Enables the trace mode and echoes the constructed Command line
to standard error before running.
|
| -x
| Stops running the xargs command if any Command line
is greater than the number of bytes specified by the -s
Size flag. This -x flag is turned on if you specify
either the -I (Uppercase i) or -l (Lowercase L)
flag. If you do not specify the -i, -I (Uppercase
i), -l (Lowercase L), -L, or-n flag, the
total length of the Command line must be within the limit specified
by the -s Size flag.
|
This command returns the following
exit values:
| 0
| All invocations of the Command parameter returned exit status
0.
|
| 1-125
| A command line meeting the specified requirements could not be assembled,
one or more of the invocations of the Command parameter returned a
non-zero exit status, or some other error occurred.
|
| 126
| Command was found but could not be invoked.
|
| 127
| Command could not be found.
|
If a command line meeting the
specified requirements cannot be assembled, the command cannot be invoked, an
invocation of the command is terminated by a signal, or an invocation of the
command exits with exit status 255. The xargs command will
write a diagnostic message and exit without processing any remaining
input.
- To use a command on
files whose names are listed in a file, enter:
xargs lint -a <cfiles
If the cfiles file contains the following text:
main.c readit.c
gettoken.c
putobj.c
the xargs command constructs and runs the following
command:
lint -a main.c readit.c gettoken.c putobj.c
If the cfiles file contains more file names than fit on a
single shell command line (up to LINE_MAX), the xargs
command runs the lint command with the file names that fit.
It then constructs and runs another lint command using the
remaining file names. Depending on the names listed in the
cfiles file, the commands might look like the following:
lint -a main.c readit.c gettoken.c . . .
lint -a getisx.c getprp.c getpid.c . . .
lint -a fltadd.c fltmult.c fltdiv.c . . .
This command sequence is not quite the same as running the
lint command once with all the file names. The
lint command checks cross-references between files. However,
in this example, it cannot check between the main.c and the
fltadd.c files, or between any two files listed on separate
command lines.
For this reason you may want to
run the command only if all the file names fit on one line. To specify
this to the xargs command use the -x flag by
entering:
xargs -x lint -a <cfiles
If all the file names in the cfiles file do not fit on one
command line, the xargs command displays an error message.
- To construct commands
that contain a certain number of file names, enter:
xargs -t -n 2 diff <<EOF
starting chap1 concepts chap2 writing
chap3
EOF
This command sequence constructs and runs diff commands
that contain two file names each (-n 2):
diff starting chap1
diff concepts chap2
diff writing chap3
The -t flag causes the xargs command to display
each command before running it, so you can see what is happening. The
<<EOF and EOF pattern-matching characters define a
here document, which uses the text entered
before the end line as standard input for the xargs command.
- To insert file names
into the middle of command lines, enter:
ls | xargs -t -I {} mv {} {}.old
This command sequence renames all files in the current directory by
adding .old to the end of each name. The
-I flag tells the xargs command to insert each line of
the ls directory listing where {} (braces) appear. If the
current directory contains the files chap1, chap2, and
chap3, this constructs the following commands:
mv chap1 chap1.old
mv chap2 chap2.old
mv chap3 chap3.old
- To run a command on
files that you select individually, enter:
ls | xargs -p -n 1 ar r lib.a
This command sequence allows you to select files to add to
the lib.a library. The
-p flag tells the xargs command to display each
ar command it constructs and to ask if you want to run it.
Enter y to run the command. Press the any other key if you
do not want to run the command.
Something similar to the following
displays:
ar r lib.a chap1 ?...
ar r lib.a chap2 ?...
ar r lib.a chap3 ?...
- To construct a command
that contains a specific number of arguments and to insert those arguments
into the middle of a command line, enter:
ls | xargs -n6 | xargs -I{} echo {} - some files in the directory
If the current directory contains files chap1 through chap10, the output
constructed will be the following:
chap1 chap2 chap3 chap4 chap5 chap6 - some files in the directory
chap7 chap8 chap9 chap10 - some file in the directory
| /usr/bin/xargs
| Contains the xargs command.
|
The ar command, diff
command, echo command, ksh command, lint
command, ls command, mv command.
Shells
Overview and Commands Overview in AIX 5L Version
5.1 System User's Guide: Operating System and
Devices.
Input and Output Handling Programmer's Overview
in AIX 5L Version 5.1 General Programming Concepts: Writing
and Debugging Programs.
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