Display filename before matching line

Question

How can I get grep to display the filename before the matching lines in its output

User · Accepted Answer

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

User · Answer

No trick necessary   grep --with-filename  pattern  file   With line numbers   grep -n --with-filename  pattern  file

User · Answer

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

User · Answer

This is a slight modification from a previous solution   My example looks for stderr redirection in bash scripts  grep  2 gt     find   -name    bash

User · Answer

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

User · Answer

grep  search this    txt   worked for me to search through all  txt files  enter your own search value  of course

[unix] Display filename before matching line

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