How can I get grep to display the filename before the matching lines in its output?
6 Answers
Try this little trick to coax grep into thinking it is dealing with multiple files, so that it displays the filename:
grep 'pattern' file /dev/null To also get the line number:
grep -n 'pattern' file /dev/null If you have the options -H and -n available (man grep is your friend):
$ cat file foo bar foobar $ grep -H foo file file:foo file:foobar $ grep -Hn foo file file:1:foo file:3:foobar Options:
-H, --with-filename
Print the file name for each match. This is the default when there is more than one file to search.
-n, --line-number
Prefix each line of output with the 1-based line number within its input file. (-n is specified by POSIX.)
-H is a GNU extension, but -n is specified by POSIX
No trick necessary.
grep --with-filename 'pattern' file With line numbers:
grep -n --with-filename 'pattern' file How about this, which I managed to achieve thanks, in part, to this post.
You want to find several files, lets say logs with different names but a pattern (e.g. filename=logfile.DATE), inside several directories with a pattern (e.g. /logsapp1, /logsapp2). Each file has a pattern you want to grep (e.g. "init time"), and you want to have the "init time" of each file, but knowing which file it belongs to.
find ./logsapp* -name logfile* | xargs -I{} grep "init time" {} \dev\null | tee outputfilename.txt Then the outputfilename.txt would be something like
./logsapp1/logfile.22102015: init time: 10ms ./logsapp1/logfile.21102015: init time: 15ms ./logsapp2/logfile.21102015: init time: 17ms ./logsapp2/logfile.22102015: init time: 11ms In general
find ./path_pattern/to_files* -name filename_pattern* | xargs -I{} grep "grep_pattern" {} \dev\null | tee outfilename.txt Explanation:
find command will search the filenames based in the pattern
then, pipe xargs -I{} will redirect the find output to the {}
which will be the input for grep ""pattern" {}
Then the trick to make grep display the filenames \dev\null
and finally, write the output in file with tee outputfile.txt
This worked for me in grep version 9.0.5 build 1989.
This is a slight modification from a previous solution. My example looks for stderr redirection in bash scripts: grep '2>' $(find . -name "*.bash")
grep 'search this' *.txt worked for me to search through all .txt files (enter your own search value, of course).
