Search file(s) for specific text.
Syntax grep <options> "Search String" [filename] grep <options> [-e PATTERN] [FILE...] grep <options> [-f FILE] [FILE...] A simple example grep "Needle in a Haystack" /etc/*
Grep searches the named input FILEs (or standard input if no files are named, or the file name - is given) for lines containing a match to the given PATTERN. By default, grep prints the matching lines.
In addition, two variant programs egrep and fgrep are available. Egrep is the same as grep -E. Fgrep is the same as grep -F.
Options -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. -b, --byte-offset Print the byte offset within the input file before each line of output. -C [NUM], -NUM, --context[=NUM] Print NUM lines (default 2) of output context. -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see below), count non-match- ing lines. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to pro- cess it. By default, ACTION is read, which means that directories are read just as if they were ordinary files. If ACTION is skip, directories are silently skipped. If ACTION is recurse, grep reads all files under each directory, recursively; this is equivalent to the -r option. -E, --extended-regexp Interpret PATTERN as an extended regular expression (see below). -e PATTERN, --regexp=PATTERN Use PATTERN as the pattern; useful to protect pat- terns beginning with -. -F, --fixed-strings Interpret PATTERN as a list of fixed strings, sepa- rated by newlines, any of which is to be matched. -f FILE, --file=FILE Obtain patterns from FILE, one per line. The empty file contains zero patterns, and therefore matches nothing. -G, --basic-regexp Interpret PATTERN as a basic regular expression (default) -H, --with-filename Print the filename for each match. -h, --no-filename Suppress the prefixing of filenames on output when multiple files are searched. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary- files=without-match option. -i, --ignore-case Ignore case distinctions in both the PATTERN and the input files. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. The scanning will stop on the first match. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. The scanning will stop on the first match. -n, --line-number Prefix each line of output with the line number within its input file. -q, --quiet, --silent Quiet; suppress normal output. The scanning will stop on the first match. Also see the -s or --no- messages option below. -r, --recursive Read all files under each directory, recursively; this is equivalent to the -d recurse option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep, traditional grep did not conform to POSIX.2, because traditional grep lacked a -q option and its -s option behaved like GNU grep's -q option. Shell scripts intended to be portable to traditional grep should avoid both -q and -s and should redirect output to /dev/null instead. -U, --binary Treat the file(s) as binary. By default, under MS- DOS and MS-Windows, grep guesses the file type by looking at the contents of the first 32KB read from the file. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -u, --unix-byte-offsets Report Unix-style byte offsets. This switch causes grep to report byte offsets as if the file were Unix-style text file, i.e., with CR characters stripped off. This will produce results identical to running grep on a Unix machine. This option has no effect unless -b option is also used; it has no effect on platforms other than MS-DOS and MS-Win- dows. -V, --version Print the version number of grep to standard error. This version number should be included in all bug reports (see below). -v, --invert-match Invert the sense of matching, to select non-match- ing lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent charac- ter. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are let- ters, digits, and the underscore. -x, --line-regexp Select only those matches that exactly match the whole line. -y Obsolete synonym for -i. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual new- line. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. --binary-files=TYPE If the first few bytes of a file indicate that the file contains binary data, assume that the file is of type TYPE. By default, TYPE is binary, and grep normally outputs either a one-line message saying that a binary file matches, or no message if there is no match. If TYPE is without-match, grep assumes that a binary file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. Warning: grep --binary-files=text might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. --help Output a brief help message. --mmap If possible, use the mmap(2) system call to read input, instead of the default read(2) system call. In some situations, --mmap yields better perfor- mance. However, --mmap can cause undefined behav- ior (including core dumps) if an input file shrinks while grep is operating, or if an I/O error occurs. Environment variables Grep's behavior can be affected by setting the following environment variables GREP_OPTIONS - default options LC_ALL, LC_MESSAGES, LANG - language for messages LC_CTYPE - foreign characters POSIXLY_CORRECT - Posix behaviour _N_GNU_nonoption_argv_flags_ - ignore an operand see `info' for more on these
Search the file example.txt, including binary data (-a) for the string 'hunting the snark':
$ sudo grep -a 'hunting the snark' example.txt
Search the whole partition (/disk0), including binary data (-a) for the string 'hunting the snark' return all the lines
starting 25 Before the text found and 50 lines After the matching text found, this can be a way to discover fragments of deleted files:
$ sudo grep -a -B 25 -A 50 'hunting the snark' /dev/disk0> results.txt
Search the file wordlist.txt for any lines that don't include at least one vowel:
$ grep -v [aeiou] wordlist.txt
Remove lines from invoices.txt if they appear in paid.txt:
$ grep -F -x -v -f paid.txt invoices.txt >paidinvoices.txt
Searching an entire hard drive with grep can be very slow, using mdfind to identify files containing text is orders of magnitude faster.
"The most dangerous of all falsehoods is a slightly distorted truth" ~ G. C. Lichtenberg
grep man page - Apple.com
awk - Find and Replace text within file(s)
mdfind - Spotlight search
tr - Translate, squeeze, and/or delete characters