grep regex whitespace behavior

Question

I have a textfile  containing something like   12 34 EUR   5 67 EUR        There is one whitespace before  EUR  and I ignore 0 XX EUR   I tried    grep   1-9  0-9    0-9   2   sEUR    gt  didn t match    grep   1-9  0-9    0-9   2   EUR    gt  worked    grep   1-9  0-9    0-9   2   s EUR    gt  worked    grep   1-9  0-9    0-9   2   s E UR     gt  worked    Can somebody explain me pls  why I can t use  s but  s  and  s E  matched   OS  Ubuntu 10 04  grep v2 5

User · Accepted Answer

This looks like a behavior difference in the handling of \s between grep 2.5 and newer versions (a bug in old grep?). I confirm your result with grep 2.5.4, but all four of your greps do work when using grep 2.6.3 (Ubuntu 10.10).

Note:

GNU grep 2.5.4
echo "foo bar" | grep "\s"
   (doesn't match)

whereas

GNU grep 2.6.3
echo "foo bar" | grep "\s"
foo bar

Probably less trouble (as \s is not documented):

Both GNU greps
echo "foo bar" | grep "[[:space:]]"
foo bar

My advice is to avoid using \s ... use [ \t]* or [[:space:]] or something like it instead.

[regex] grep regex whitespace behavior

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