Normally when you run on a group of files, the output lists the filename along with the line containing the search pattern. Sometimes you want to know only the names of the files, and you don't care to know the line (or lines) that match. In this case, use the -l (lowercase letter "l") option to list only filenames where matches occur. For example, the command:
grep -l R5
file1 file2 ...
searches the files for a line containing the string
produces a list of those filenames, and
stores the list in r5.filelist. (This list might represent the files
containing Release 5 documentation of a particular product.) Because these
Release 5 files can now be referenced by one list, you can treat them as a
single entity and run various commands on them all at once:
You don't have to create a file list, though.
You can insert the output of a grep directly into a command line
with command substitution.
For example, to edit only the subset of files containing
R5, you would type:
vi `grep -l R5
grep -l is also good for shell programs that need to check whether a file contains a particular string. The traditional way to do that test is by throwing away grep's output and checking its exit status:
something somefile>/dev/null then ...
If somefile is huge, though, grep has to search all of it. Adding the grep -l option saves time because grep can stop searching after it finds the first matching line.
|15.6 Maybe You Shouldn't Use Wildcards in Pathnames||15.8 Getting a List of Non-Matching Files with grep -c|