sed and grep get the line number for a match

Question

I have a log file and i use sed to extract the lines between two strings which contains the word MATCH. I use sed to extract the lines and grep to only take the lines containing the word "MATCH". I would need the lines number in the log file where a match is found.

Date:...
TST STARTS
DISCARD str1
DISCARD str2
MATCH str3 //line 5
MATCH str4 //line 6
DISCARD str5
TST FINISHED

I use this command to extract the lines:

sed -n "/TST STARTS/,/TST FINISHED/p" log.txt | grep "MATCHED".

My output is:

MATCH str3
MATCH str4

But I also need in the output the lines number:

line 5: MATCH str3
line 6: MATCH str4

Answer 1

You could use:

cat -n

to number the lines before you apply your sed, like this:

cat -n log.txt | sed -n "/TST STARTS/,/TST FINISHED/p" | grep "MATCHED"

Alternatively, you could replace cat -n with a variant of nl:

nl -n ln log.txt | sed ...

Answer 2

My first attempt wasn't keeping the line number, because the sed part removes certain lines.

Everything can be done with this awk:

$ awk '/TST STARTS/ {p=1} p && /MATCH/ {print "line "NR" --> "$0}; /TST FINISHED/ {p=0}' a
line 5 --> MATCH str3 //line 5
line 6 --> MATCH str4 //line 6

• '/TST STARTS/ {p=1} sets a flag p=1 so that from now on all lines will be taken into account.
• p && /MATCH/ {print "line "NR" --> "$0} if the flag p is active and the line contains MATCH, then it prints the info.
• /TST FINISHED/ {p=0} turns the flag off when finding TST FINISHED text.