grep leading space in text file

micyew · 10-01-2014, 12:51 AM

Hi,

Need some advice from some regex gurus...

I've this text file and would like to grep the line with 3 leading spaces...How would I do it?

I tried grep "^\s[3]" a.txt but fail....Tried grep "^[:space]{3}" a.txt also fail...

Any idea??

cat <<< 3 leading spaces
cat
cat
cat <<< 3 leading spaces
cat
cat

pan64 · 10-01-2014, 01:01 AM

would be nice to read about regexps. But this one is quite easy:

Code:

grep '^   '     ( that is a ^ and 3 spaces ). 
      ....

Why do you want to make it difficult?

astrogeek · 10-01-2014, 01:09 AM

Quote:

Originally Posted by micyew

Hi,

Need some advice from some regex gurus...

I've this text file and would like to grep the line with 3 leading spaces...How would I do it?

I tried grep "^\s[3]" a.txt but fail....Tried grep "^[:space]{3}" a.txt also fail...

If that is the only criteria, how about:

Code:

 grep '^   ' a.txt

...where there are three spaces after the caret?

*** pan64 types faster than I do!

syg00 · 10-01-2014, 01:09 AM

Read the manpage.
Character classes need two square brackets - also pays to try "grep -E ..." when regex seems to be mis-behaving.

pan64 · 10-01-2014, 01:21 AM

Quote:

Originally Posted by astrogeek

If that is the only criteria, how about:

Code:

 grep '^   ' a.txt

...where there are three spaces after the caret?

*** pan64 types faster than I do!

(or less...)

Otherwise

Code:

grep -E '^\s{3}'
grep -E '^[[:space:]]{3}'

should work too. you can try online regexp checkers, nowadays they also explain that expression

micyew · 10-01-2014, 04:49 PM

Hi all,

thanks for the response. ...I did try all recommendation. ..but it out all 'cat', not the 3 leading space cat....Did you try out? If yes could cut/paste thr result so that I can see the difference. ...thanks. ..

micyew · 10-01-2014, 05:55 PM

Hi all,

Only this works....Thanks alot for the hints....

grep -E '^[[:space:]]{3}cat' a.txt

pan64 · 10-02-2014, 12:34 AM

next time please use [code]here comes your code[/code] to keep formatting. I have just understood your first post.
From the other hand:

Code:

grep -E '^   cat'
grep -E '^\s{3}cat'
grep -E '^[[:space:]]{3}cat'

all should work - at least works for me worked. Probably you mistyped something or there is no space but something else....?

If you really want to say thanks just press YES.