If I type:

:echo system('grep -IRn foobar ~/.vim | grep -v backup')

Vim displays the output of the shell command:
$ grep -IRn foobar ~/.vim | grep -v backup

Which is the list of files containing the pattern foobar inside the folder ~/.vim, after removing the matches containing the pattern backup.

:echo expand('`grep -IRn foobar ~/.vim | grep -v backup`')

Vim does the same thing (without the newline at the end).

:e `=system('grep -IRn foobar ~/.vim | grep -v backup | tail -1 | cut -d: -f1')`

Vim edits the last file from the output of the previous shell command.

The last 3 commands work without escaping the pipe. The latter is never interpreted as a command termination, probably because it's protected by the string. Maybe for the same reason this command works:

:echo 'hello | world'

But If I want to populate the quickfix list with the same shell command and I type:

:cexpr system('grep -IRn foobar ~/.vim | grep -v backup')

I have the following errors:

E115: Missing quote: 'grep -IRn foobar ~/.vim 
E116: Invalid arguments for function system('grep -IRn foobar ~/.vim 
E15: Invalid expression: system('grep -IRn foobar ~/.vim 

It seems that the pipe was interpreted as a command termination, and that it must be escaped:

:cexpr system('grep -IRn foobar ~/.vim \| grep -v backup')

The pipe is inside a string, and the command is almost identical to the first one with :echo where the pipe is not escaped.

Why is it suddenly interpreted as a command termination with :cexpr system('shell cmd')?

  • 2
    Strange error, for what it's worth, can you confirm that if you do let a='grep -IRn foobar ~/.vim | grep -v backup' and then :cexpr system(a) it works ?
    – nobe4
    May 7, 2016 at 16:45
  • 1
    I suspect that for cexpr, the | is used to delimit the vim expression, and not the system one. so vim try to run cexpr system('grep -IRn foobar ~/.vim and then grep -v backup'), which of course fail.
    – nobe4
    May 7, 2016 at 16:53
  • 1
    I thought I found something looking at :h :bar, it seems that there are special cases for |, but unfortunately it does not match your problem...
    – nobe4
    May 7, 2016 at 17:06
  • 1
    You're welcome, considere adding this + some informations as an answer for further reference :)
    – nobe4
    May 7, 2016 at 19:44
  • 1
    @user9433424 you can get around having to use a variable by doing execute "cexpr " . system("...")
    – Ingo
    Aug 23, 2016 at 18:28

1 Answer 1


This was changed in 8.1.2401; now a shell pipe character does not need to be escaped anymore inside an expression containing a quoted shell command after :cexpr and the five other variants:


Before the patch, an unescaped shell pipe would raise E115 and E116:

$ vim -Nu NONE
:cexpr system('grep -Rn grail '..$VIMRUNTIME..' | grep -v tag')
E115: Missing quote: '
E116: Invalid arguments for function system('grep -Rn grail '..$VIMRUNTIME..'

Now, the same command edits the file $VIMRUNTIME/doc/index.txt, and populates the quickfix list with this entry:

{'lnum': 1121,
 'bufnr': 2,
 'col': 0,
 'pattern': '',
 'valid': 1,
 'vcol': 0,
 'nr': -1,
 'type': '',
 'module': '',
 'text': 'You found it, Arthur!                         *holy-grail* *:smile*'}

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