Just as you can run a compiler from Emacs and then visit the lines with compilation errors, you can also run grep and then visit the lines on which matches were found. This works by treating the matches reported by grep as if they were errors. The output buffer uses Grep mode, which is a variant of Compilation mode (see Compilation Mode).
find, and collect output in the *grep* buffer.
zgrepand collect output in the *grep* buffer.
To run grep, type M-x grep, then enter a command line that specifies how to run grep. Use the same arguments you would give grep when running it normally: a grep-style regexp (usually in single-quotes to quote the shell's special characters) followed by file names, which may use wildcards. If you specify a prefix argument for M-x grep, it finds the identifier (see Xref) in the buffer around point, and puts that into the default grep command.
Your command need not simply run grep; you can use any shell command that produces output in the same format. For instance, you can chain grep commands, like this:
grep -nH -e foo *.el | grep bar | grep toto
The output from grep goes in the *grep* buffer. You can find the corresponding lines in the original files using C-x `, <RET>, and so forth, just like compilation errors.
Some grep programs accept a ‘--color’ option to output special
markers around matches for the purpose of highlighting. You can make
use of this feature by setting
t. When displaying a match in the source buffer, the exact
match will be highlighted, instead of the entire source line.
The command M-x grep-find (also available as M-x
find-grep) is similar to M-x grep, but it supplies a different
initial default for the command—one that runs both
grep, so as to search every file in a directory tree. See also
find-grep-dired command, in Dired and Find.
The commands M-x lgrep (local grep) and M-x rgrep
(recursive grep) are more user-friendly versions of grep and
grep-find, which prompt separately for the regular expression
to match, the files to search, and the base directory for the search.
Case sensitivity of the search is controlled by the current value of
case-fold-search. The command M-x zrgrep is similar to
M-x rgrep, but it calls zgrep instead of
grep to search the contents of gzipped files.
These commands build the shell commands based on the variables
rgrep). The files to search can use aliases defined in
Directories listed in the variable
grep-find-ignored-directories are automatically skipped by
M-x rgrep. The default value includes the data directories used
by various version control systems.