CODEWITHSUNDEEP
linuxgreptailhead
avanabana
avanabana

Reputation: 41

grep tail and head wrong result

I want to show the 3 first lines and the 2 last lines that contain a word. I tried a grep command but it's not showing what I want.

grep -w it /usr/include/stdio.h | head -3 | tail -2

It only display the 2nd and 3nd lines that contain "it" in it.

Upvotes: 3

Views: 8745

Answers (4)

KitCarson
KitCarson

Reputation: 1

cat /usr/include/stdio.h | grep -w it | head -3 | tail -2

Upvotes: 0

yoga
yoga

Reputation: 860

you should try this 

grep -A 2 -B 3 "it" /usr/include/stdio.h

-A = After context of 2 lines to the matching word "it"

-B = After context of 3 lines to the matching word "it"

you can also add -W if you really need a regex.

expected output:

line 1

line 2

line that contains it

line 4

line 5

line 6

Upvotes: 0

Mahmoud
Mahmoud

Reputation: 31

You can simply append the results of head and tail : 

{ head -3 ; tail -2 ;} < /usr/include/stdio.h

Upvotes: 2

Thor
Thor

Reputation: 47099

The issue here is that tail never receives the output of grep, but rather only the first 3 lines of the file. To make this work reliably you either need to grep twice, once with head and once with tail or multiplex the stream, e.g.:

grep -w it /usr/include/stdio.h |
tee >(head -n3 > head-of-file) >(tail -n2 > tail-of-file) > /dev/null
cat head-of-file tail-of-file

Output here:

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   The GNU C Library is distributed in the hope that it will be useful,
   or due to the implementation it is a cancellation point and
/* Try to acquire ownership of STREAM but do not block if it is not

Upvotes: 2

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