Use grep to report back only line numbers
GrepGrep Problem Overview
I have a file that possibly contains bad formatting (in this case, the occurrence of the pattern \\backslash
). I would like to use grep
to return only the line numbers where this occurs (as in, the match was here, go to line # x and fix it).
However, there doesn't seem to be a way to print the line number (grep -n
) and not the match or line itself.
I can use another regex to extract the line numbers, but I want to make sure grep cannot do it by itself. grep -no
comes closest, I think, but still displays the match.
Grep Solutions
Solution 1 - Grep
try:
grep -n "text to find" file.ext | cut -f1 -d:
Solution 2 - Grep
If you're open to using AWK:
awk '/textstring/ {print FNR}' textfile
In this case, FNR is the line number. AWK is a great tool when you're looking at grep|cut, or any time you're looking to take grep output and manipulate it.
Solution 3 - Grep
All of these answers require grep to generate the entire matching lines, then pipe it to another program. If your lines are very long, it might be more efficient to use just sed to output the line numbers:
sed -n '/pattern/=' filename
Solution 4 - Grep
Bash version
lineno=$(grep -n "pattern" filename)
lineno=${lineno%%:*}
Solution 5 - Grep
I recommend the answers with sed
and awk
for just getting the line number, rather than using grep
to get the entire matching line and then removing that from the output with cut
or another tool. For completeness, you can also use Perl:
perl -nE '/pattern/ && say $.' filename
or Ruby:
ruby -ne 'puts $. if /pattern/' filename
Solution 6 - Grep
You're going to want the second field after the colon, not the first.
grep -n "text to find" file.txt | cut -f2 -d:
Solution 7 - Grep
To count the number of lines matched the pattern:
grep -n "Pattern" in_file.ext | wc -l
To extract matched pattern
sed -n '/pattern/p' file.est
To display line numbers on which pattern was matched
grep -n "pattern" file.ext | cut -f1 -d:
Solution 8 - Grep
using only grep:
grep -n "text to find" file.ext | grep -Po '^[^:]+'