How can I make grep print the lines below and above each matching line?

Question

I have to parse a very large file and I want to use the command grep (or any other tool).

I want to search each log line for the word FAILED, then print the line above and below each matching line, as well as the matching line.

For example:

id : 15
Satus : SUCCESS
Message : no problem

id : 15
Satus : FAILED
Message : connection error

And I need to print:

id : 15
Satus : FAILED
Message : connection error

score 871 · Accepted Answer · edited Mar 02 '19 at 09:47

871

grep's -A 1 option will give you one line after; -B 1 will give you one line before; and -C 1 combines both to give you one line both before and after, -1 does the same.

edited Mar 02 '19 at 09:47

webaholik

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answered Jul 02 '09 at 05:35

pgs

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+1, I forgot about -C (lines of context) – Milan Babuškov Jul 02 '09 at 07:10
3

@StevenLu, but only for the duration of `grep` so prepare a long input. – Maciej Gol Jul 12 '14 at 19:05
1

perfect for searching fasta for header and getting sequence (if it's a one-liner fasta) – st.ph.n Sep 15 '16 at 20:21
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You're a wizard – Kyle Bridenstine Jul 31 '19 at 15:20
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Me, patting myself on the back whenever I need to use one of these flags: "`-A` could stand for 'above' or 'after' and `-B` could stand for 'below' or 'before'. Hmm...clearly the most reasonable choice is 'above' and 'below' since that's how they appear on the screen, plus it makes sense alphabetically." – Mike S Dec 12 '19 at 00:39

score 61 · Answer 2 · edited Mar 02 '19 at 09:45

61

Use -B, -A or -C option

grep --help
...
-B, --before-context=NUM  print NUM lines of leading context
-A, --after-context=NUM   print NUM lines of trailing context
-C, --context=NUM         print NUM lines of output context
-NUM                      same as --context=NUM
...

edited Mar 02 '19 at 09:45

webaholik

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answered Jul 02 '09 at 05:29

tefozi

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Amusing that this is the output of `grep --help | grep context` – Arkaine55 Jul 21 '19 at 02:43

score 43 · Answer 3 · answered Jul 02 '09 at 05:28

43

Use -A and -B switches (mean lines-after and lines-before):

grep -A 1 -B 1 FAILED file.txt

answered Jul 02 '09 at 05:28

Milan Babuškov

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How can I make grep print the lines below and above each matching line?

For example:

3 Answers3

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