How can I can I find files that contain a specific pattern on a specific line number ? Let's assume I have a directory with a bunch of text files containing 3 lines, such as:
Title A
Category X
Description Y
How can I grep / filter every files that have Category X on line 2?
How can I find files that have Title A as line 1?
I looked at the grep man page, ripgrep and alternative but not sure you can limit the search of a pattern to specific line numbers.
You can use awk like that:
awk 'FNR == 2 && /Category X/ {print FILENAME}' *
Your can use find with awk in order to exit processing the rest of the file when pattern found in the 2nd line, or even also exit if it was not found that in the 2nd line.
find -type f -name 'xyz*.txt' -exec \
awk 'NR==2{ if(/pattern/) print FILENANE; exit }' {} \;
grep only, for the fun of it:
PAT="Category X"
LN=2
> grep -n "$PAT" file* | grep ":$LN:$PAT$" | grep -o "^[^:]*"
file1
file2
To test just the files in your current directory (assuming there's no sub-dirs or unreadable files in this directory and not so many as to exceed ARGS_MAX) would be:
awk 'FNR==2{ if (/Category X/) print FILENAME; nextfile }' *
but from your comments it sounds like you want to descend a hierarchy which would be:
find . -type f -exec \
awk 'FNR==2{ if (/Category X/) print FILENAME; nextfile }' {} +
The use of + in the find command (may require GNU find) will cause it to run awk on batches of files instead of 1 at a time, and the use of nextfile (if your awk supports it - many do, some don't) will cause awk to stop reading the current file and move on to the next one once the 2nd line is read. Since your input files are each only 3 lines long it'll be very efficient whether your awk supports nextfile or not.
GNU grep can be used for your use case:
$ grep -Plzr '^(?:.*\n){1}.*Category X' .
grep normally works on a per-line basis, but GNU grep has added the -z option where in it treats the whole file as a line because it separates records on a character NOT found in text files (\0).
So now we can apply the regex on the whole file. Your requirement is searching only the second line, hence we drive past one line without doing anything ^(?:.*\n){1}
The caret ^ anchors the regex to begin from the beginning. The dot can not span lines because it doesn't match a newline.
Then the .*Category X will start looking in the next line, meaning the second, but won't span lines , so it matches if the pattern is found on the second line.
If there's a match, the -l option will list out the filename to STDOUT.
The -r option will make grep run recursively (GNU feature).
The -P will enable to write Perl style regexes (GNU feature).
Here is another stab at the problem, with GNU find+sed combo:
$ find . -type f -exec sed -ns '2{/Category X/F;}' {} +
GNU find + GNU xargs feed into Perl can also do it:
find . -type f ! -size 0 -print0 |
xargs -r0 perl -lne '
(eof||$.==2)&&do{
print $ARGV if $.==2 && /Category X/;
close ARGV; undef $.;
};
'
