After a pipe the command is considered prefixed with a space

Question

Sometimes on my terminal (Ubuntu) when I type:

ls | grep toto

I get this error:

 grep: command not found*

Notice that the shell is writing grep prefixed by a space. How can this be possible?

It is very strange. Also, note that you can do the same with `ls *toto*` — fedorqui, Nov 15 '13 at 11:11
Can you reliably reproduce it? Is ls | grep something the only thing on the command-line? This looks like there's a quote somewhere, escaping the initial space. — rbp, Nov 15 '13 at 11:13
Is this some sort of special whitespace? Non-breaking space, narrow space, etc. — knittl, Nov 15 '13 at 11:42
What is the value of the `PATH` (the output of `echo $PATH`) when you get that error? — Radu Rădeanu, Nov 15 '13 at 12:09
echo $PATH is the same when the error occurs than when it does not — user2854544, Nov 15 '13 at 12:32
@user2854544, I can only reproduce that error with `ls |\ grep toto`. Is it possible that your terminal is sending something other than an actual *space*, like some space-like [Unicode character](http://en.wikipedia.org/wiki/Whitespace_character#Unicode)? — ghoti, Nov 15 '13 at 12:38

score 28 · Accepted Answer · edited May 23 '17 at 12:17

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<pre style="width:650px; white-space:pre-wrap">Sometimes on my terminal (Ubuntu) when I type :

ls |&#160;grep toto

Thank you for copy-pasting the actual line! (But you didn't copy-paste the error message, naughty you!) See the problem? You have an unbreakable space after the pipe symbol. Shells only understand ASCII characters; all non-ASCII characters, including U+00A0 NO-BREAK SPACE, are treated as word constituents, so that unbreakable space is treated as part of the word that's in command name position.

You're presumably using a keyboard layout where you need to hold down AltGr to type |. Make sure to release the AltGr modifier so as not to accidentally type AltGr+Space instead of Space. Note that you don't need a space there, you can type ls |grep toto if that's easier on your fingers.

edited May 23 '17 at 12:17

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answered Nov 15 '13 at 12:51

Gilles 'SO- stop being evil'

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Arguably. Bash's parser ought to canonicalize non-breaking space to regular space. – tripleee Dec 23 '13 at 09:03
@tripleee That would be tricky: bash would have to assume that the encoding of the string matches the encoding specified by the locale, which isn't always the case in practice and would break some existing applications. – Gilles 'SO- stop being evil' Dec 23 '13 at 13:24
Thanks a lot for the answer. I thought it was a bug until now. – ling Nov 03 '14 at 20:51
My problem, for the record, was actually `Shift + Space` (my pipe character requires `shift`) – jcuenod Feb 20 '15 at 15:09

score 6 · Answer 2 · answered Dec 23 '13 at 08:59

To complete Gilles answer, you can disable this behavior in Ubuntu/Gnome by replacing non-breakable space character by usual space in keyboard layout settings.

Settings -> Keyboard -> Layout -> Options, and select "Using space key to input non-breakable space character" and set it to: "Usual space at any level".

Or from the command line

setxkbmap -option "nbsp:none"

I found this fix in http://my.opera.com/nicomen/blog/unrecognized-character-xc2.

This was also annoying on French keyboard for Perl scripts when using curly brackets or in Python when using hash sign for comments followed by a space.

Also https://stackoverflow.com/questions/8694442/bash-piping-in-osx-prompts-command-not-found-sometimes which has a nice alternative workaround which doesn't depend on X. — tripleee, Nov 14 '17 at 13:00

After a pipe the command is considered prefixed with a space

2 Answers2