grep is used to search for PATTERN in each FILE or standard input. PATTERN is, by default, a basic regular expression (BRE).

Example: grep -i ‘hello world’ menu.h main.c

Usage: grep [OPTION]… PATTERN [FILE]…

Regexp selection and interpretation:
-E, –extended-regexp PATTERN is an extended regular expression (ERE)
-F, –fixed-strings PATTERN is a set of newline-separated strings
-G, –basic-regexp PATTERN is a basic regular expression (BRE)
-P, –perl-regexp PATTERN is a Perl regular expression
-e, –regexp=PATTERN use PATTERN for matching
-f, –file=FILE obtain PATTERN from FILE
-i, –ignore-case ignore case distinctions
-w, –word-regexp force PATTERN to match only whole words
-x, –line-regexp force PATTERN to match only whole lines
-z, –null-data a data line ends in 0 byte, not newline

-s, –no-messages suppress error messages
-v, –invert-match select non-matching lines
-V, –version display version information and exit
–help display this help text and exit

Output control:
-m, –max-count=NUM stop after NUM matches
-b, –byte-offset print the byte offset with output lines
-n, –line-number print line number with output lines
–line-buffered flush output on every line
-H, –with-filename print the file name for each match
-h, –no-filename suppress the file name prefix on output
–label=LABEL use LABEL as the standard input file name prefix
-o, –only-matching show only the part of a line matching PATTERN
-q, –quiet, –silent suppress all normal output
–binary-files=TYPE assume that binary files are TYPE;
TYPE is ‘binary’, ‘text’, or ‘without-match’
-a, –text equivalent to –binary-files=text
-I equivalent to –binary-files=without-match
-d, –directories=ACTION how to handle directories;
ACTION is ‘read’, ‘recurse’, or ‘skip’
-D, –devices=ACTION how to handle devices, FIFOs and sockets;
ACTION is ‘read’ or ‘skip’
-r, –recursive like –directories=recurse
-R, –dereference-recursive likewise, but follow all symlinks
–include=FILE_PATTERN search only files that match FILE_PATTERN
–exclude=FILE_PATTERN skip files and directories matching FILE_PATTERN
–exclude-from=FILE skip files matching any file pattern from FILE
–exclude-dir=PATTERN directories that match PATTERN will be skipped.
-L, –files-without-match print only names of FILEs containing no match
-l, –files-with-matches print only names of FILEs containing matches
-c, –count print only a count of matching lines per FILE
-T, –initial-tab make tabs line up (if needed)
-Z, –null print 0 byte after FILE name

Context control:
-B, –before-context=NUM print NUM lines of leading context
-A, –after-context=NUM print NUM lines of trailing context
-C, –context=NUM print NUM lines of output context
-NUM same as –context=NUM
–colour[=WHEN] use markers to highlight the matching strings; WHEN is ‘always’, ‘never’, or ‘auto’
-U, –binary do not strip CR characters at EOL (MSDOS/Windows)
-u, –unix-byte-offsets report offsets as if CRs were not there

‘egrep’ means ‘grep -E’. ‘fgrep’ means ‘grep -F’. Direct invocation as either ‘egrep’ or ‘fgrep’ is deprecated. When FILE is -, read standard input. With no FILE, read . if a command-line -r is given, – otherwise. If fewer than two FILEs are given, assume -h. Exit status is 0 if any line is selected, 1 otherwise; if any error occurs and -q is not given, the exit status is 2.

Categories: Reference