50

Is it possible to make xargs use only newline as separator? (in bash on Linux and OS X if that matters)

I know -0 can be used, but it's PITA as not every command supports NUL-delimited output.

  • What is it that you're trying to accomplish. There may be another way to go about it. – Paused until further notice. Mar 31 '10 at 4:50
  • @Dennis I use it for various things, often in pipeline with grep, sed, very basic awk etc., mostly to parallelize execution. find -print0 -name \*.foo -maxdepth 1 | xargs -0 -P4 is way too much to type compared with ls *.foo | xargs -P4. – Kornel Mar 31 '10 at 13:21
  • Scripts and functions are two excellent ways to reduce typing. – Paused until further notice. Mar 31 '10 at 13:49
  • This is an SO question, isn't it? – Charles Stewart Apr 1 '10 at 11:22
22

Something along the lines of

alias myxargs='perl -p -e "s/\n/\0/;" | xargs -0'
cat nonzerofile | myxargs command

should work.

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  • 47
    tr '\n' '\0' works too. – Kornel Apr 5 '10 at 15:26
  • 2
    perl is overkill for a single character. tr is faster both for the cpu and for your fingers. – Hello World Apr 23 '15 at 20:09
  • When the only tool you know is radioactive decay, everything looks like a nuclear reactor – Ray Foss Sep 11 at 8:49
62

GNU xargs (default on Linux; install findutils from MacPorts on OS X to get it) supports -d which lets you specify a custom delimiter for input, so you can do

ls *foo | xargs -d '\n' -P4 foo 
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  • I have alias xxargs="xargs -d '\n'" in my bashrc. So I can just do things like this: grep -IRl foo | xxargs sed -i s/foo/bar/g – tylerl Feb 13 '11 at 0:45
  • 5
    This really should be the accepted answer. No need to break out perl. Though tr is a good idea too. – Ehtesh Choudhury Dec 3 '12 at 18:36
  • 4
    brew install findutils and gxargs was exactly what I needed on OS X, thanks. – Brad Koch Mar 22 '16 at 19:00
6

With Bash, I generally prefer to avoid xargs for anything the least bit tricky, in favour of while-read loops. For your question, while read -ar LINE; do ...; done does the job (remember to use array syntax with LINE, e.g., ${LINE[@]} for the whole line). This doesn't need any trickery: by default read uses just \n as the line terminator character.

I should post a question on SO about the pros & cons of xargs vs. while-read loops... done!

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  • 2
    This can only emulate xargs -n1 -d'\n', and not the whole xargs. – Hello World Apr 23 '15 at 20:12
  • @HelloWorld - You can bunch arguments together easily enough, so you can simulate xargs -n$N as well with only a bit of extra scripting. – Charles Stewart May 5 '15 at 16:33
  • Yes, I'm among the upvoters, it's just a remark worth mentioning. – Hello World May 9 '15 at 10:43
  • This is exactly what I do! Plus, you can use the read options, like reading more words in separate variables, or change delimiter with IFS=' '. – caesarsol Mar 13 '17 at 14:14
1
$ echo "1\n2 3\n4 5 6" | xargs -L1 echo  "#"
# 1
# 2 3
# 4 5 6
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0

please use the -d option of xargs

  --delimiter=delim, -d delim

Input items are terminated by the specified character. The specified delimiter may be a single character, a C-style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible.

Example:

$ echo 'for arg in "$@"; do echo "arg: <$arg>"; done' > show_args
$ printf "a a\nb b\nc c\n"
a a
b b
c c
$ printf "a a\nb b\nc c\n" | xargs -d '\n' bash show_args
arg: <a a>
arg: <b b>
arg: <c c>
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-2

What about cat file | xargs | sed 's/ /\n/ig' this will convert spaces to newlines, using standard Linux bash tools.

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  • If file contains spaces and newlines, then the result of this command will make it impossible to distinguish between them, which seems to be going in the opposite direction of what this question asks for – Max Nanasy Sep 24 '18 at 19:07

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