Linux Command - xargs

The xargs command is used to send batches of arguments to a command. The command is run for each batch.

Problem - Why this functionality is needed:

• Commands can only support a limited number of arguments ( argument length limit for exec less some ).
• Running a command once per argument would be very slow.

Behavior:

• takes list of items from standard input
• passed to the command specified in batches
  • default command: echo
  • batch size: sysem defined

NOTE - xargs won’t handle filenames with spaces correctly. The ‘-0’ option can be used to split on nulls instead. This will require the input to be split by nulls. ( The GNU find command does this with ‘-print0’).

Generated a sequence of numbers and pass it to xargs as a test:

seq 1 100 | xargs

echo the names of all listed files:

ls /data1 | xargs

Remove all files listed:

find /data1 | xargs rm

grep for a string inside all files found:

find /data1 | xargs grep "Error"

grep for a string inside all files found while also handling filenames with spaces by using the “-print0” and “-0” options of the find and xargs commands:

find /data1 -print0 | xargs -0 grep "Error"

gzip all files listed:

ls *.txt | xargs gzip

gzip all files found:

find /data1 | xargs gzip

gzip all files found and do as many in parallel as possible ( 0 ):

find /data1 | xargs -P 0 gzip

Using a replace string to control arg placement:

seq 1 5 | xargs -I STRING echo "start:" STRING "end"

Use a file instead of standard input:

xargs -a my_list.txt rm

Show system limits:

echo /dev/null | xargs --show-limits

-0	split on null
-a	file # read from file
-I	replace-str
-n	max_args
-P	max processes to run in parallel ( default 1 ), set to 0 for max possible
-p	interactive, prompt before running each command
-r	don’t run if no args ( GNU only )
–show-limits	shows system limits