xargs howto
Edit me

xargs

=========
xargs takes items from stdin, delimited by blanks / newlines, and executes the command (default /bin/echo) one or more times. Blank lines on the standard input are ignored.

Processing sequence for xargs:

  • split
  • batch
  • send to parameters of following cmd

split

  • -0
    Input items are splitted by \0 instead of by whitespace. The GNU find -print0 option produces input suitable for this mode.

  • -d delim
    Input items are splitte by specified delim. Multibyte characters are NOT supported.

batch

  • -n n
    maximum n results after splitted will be in a batch, and every batch will be appended a ‘\n’ during print
$ ls
a  b  c  d  logdir  one space.log  shdir  test  vmware-root

$ ls | xargs -d o | sed -ne 'l'
a$
b$
c$
d$
l gdir$
 ne space.l g$
shdir$
test$
vmware-r  t$
$

# batch 1:
# a 
# b
# c
# d
# lo
# batch 2:
# gdir
# o
# print result:
# a
# b
# c
# d
# l[o] gdir
# [o]\n

# batch 3:
# ne space.lo
# batch 4:
# g
# shdir
# test
# vmware-ro
# print result: 
# ne space.l[o]g
# shdir
# test
# vmware-r[o]\n

# batch 5:
# o
# batch 6:
# t
# print result: 
# [o]t\n

$ ls | xargs -d o -n 2 | sed -ne 'l'
a$
b$
c$
d$
l gdir$
$
ne space.l g$
shdir$
test$
vmware-r$
 t$
$
  • -L n
    maximum n lines after splitted will be in a batch

send

  • -i
    replace occurrences of {} with batch sent 
    $ find . -type f -name abc | xargs -i ls -al {} {}
-rw-rw-r-- 1 jun_zou jun_zou 0 Mar  4 20:20 ./abc
-rw-rw-r-- 1 jun_zou jun_zou 0 Mar  4 20:20 ./abc
  • -I replace-str
    replace occurrences of replace-str with batch sent, and replace-str 
    $ find . -type f -name abc | xargs -I arg ls -al arg arg
-rw-rw-r-- 1 jun_zou jun_zou 0 Mar  4 20:20 ./abc
-rw-rw-r-- 1 jun_zou jun_zou 0 Mar  4 20:20 ./abc

misc

  • -t
    Print the command line on stderr before executing it

  • -p
    interactive run mode

  • -P max-procs
    parrellel run max-procs processes; the default is 1

Tags: bash