GREP(1) GREP(1) NAME grep - search a file for a pattern SYNOPSIS grep [-E| -F] [-c| -l| -q] [-bhinsvxyC] -e pattern_list [-f pattern_file]. . .[file . . .] grep [-E| -F] [-c| -l| -q] [-bhinsvxyC][-e pattern_list] -f pattern_file]. . .[file . . .] grep [-E| -F] [-c| -l| -q] [-bhinsvxyC] pattern_list[file . . .] DESCRIPTION The grep utility searches the input files, selecting lines matching one or more patterns; the types of patterns are controlled by the options specified. The patterns are specified by the -e option, -f option, or the pattern_list operand. The pattern_list's value consists of one or more patterns separated by newline characters; the pattern_file's contents consist of one or more patterns terminated by newline characters. By default, an input line will be selected if any pattern, treated as an entire basic regular expression (BRE) as described in the regcomp(5) man page under the section titled: Basic Regular Expressions, matches any part of the line; a null BRE will match every line. By default, each selected input line will be written to the standard output. Regular expression matching will be based on text lines. Since a newline character separates or terminates patterns (see the -e and -f options below), regular expressions cannot contain a newline character. Similarly, since patterns are matched against individual lines of the input, there is no way for a pattern to match a newline character found in the input. Command line options are: -E Match using extended regular expressions. Treat each pattern specified as an ERE, as described in the regcomp(5) man page under the section titled: Extended Regular Expressions. If any entire ERE pattern matches an input line, the line will be matched. A null ERE matches every line. -F Match using fixed strings. Treat each pattern specified as a string instead of a regular expression. If an input line contains any of the patterns as a contiguous sequence of bytes, the line will be matched. A null string matches every line. -b Precede each output line by the block number within the input file where it was found. The first (512 byte) block is number 0. -c Write only a count of selected lines to standard output. -e pattern_list Specify one or more patterns to be used during the search for input. Patterns in pattern_list must be separated by a newline character. A null pattern can be specified by two adjacent newline characters in pattern_list. Unless the -E or -F option is also specified, each pattern will be treated as a BRE, as described in the regcomp(5) man page under the section titled: Basic Regular Expressions. Multiple -e and -f options are accepted by the grep utility. All of the specified patterns are used when matching lines, but the order of evaluation is unspecified. -f pattern_file Read one or more patterns from the file named by the pathname pattern_file. Patterns in pattern_file are terminated by a newline character. A null pattern can be specified by an empty line in pattern_file. Unless the -E or -F option is also specified, each pattern will be treated as a BRE, as described in the regcomp(5) man page under the section titled: Basic Regular Expressions. -h Suppress the name of the file containing the matching line from being printed on output when multiple files are searched. -i Perform pattern matching in searches without regard to case. See the regcomp(5) man page under the section titled: Regular Expression General Requirements. -l Write only the names of files containing selected lines to standard output. Pathnames are written once per file searched. If the standard input is searched, a pathname of "(standard input)" will be written, in the POSIX locale. In other locales, standard input may be replaced by something more appropriate in those locales. -n Precede each output line by its relative line number in the file, each file starting at line 1. The line number counter will be reset for each file processed. -q Quiet. Do not write anything to the standard output, regardless of matching lines. Exit with zero status if an input line is selected. -s Suppress the error messages ordinarily written for non-existent or unreadable files. Other error messages will not be suppressed. -v Select lines not matching any of the specified patterns. If the -v option is not specified, selected lines will be those that match any of the specified patterns. -x Consider only input lines that use all characters in the line to match an entire fixed string or regular expression to be matching lines. -y Obsolescent option. Same as -i. -C Obsolete option. Unused. OPERANDS The following operands are supported: pattern Specify one or more patterns to be used during the search for input. This operand is treated as if it were specified as -e pattern_list. file A pathname of a file to be searched for the patterns. If no file operands are specified, the standard input will be used. STDIN The standard input will be used only if no file operands are specified. See INPUT FILES. INPUT FILES The input files must be text files. STDOUT If the -l option is in effect, and the -q option is not, the following will be written for each file containing at least one selected input line: "%s\n", file Otherwise, if more than one file argument appears, and the -q and -h options are not set, the grep utility will prefix each output line by: "%s:", file The remainder of each output line depends on the other options specified: o If the -c option is in effect, the remainder of each output line will contain: "%d\n", <count> o If -c is not in effect and the -n option is in effect, the grep utility will prefix each output line by: "%d:", <line number> o If -c is not in effect and the -b option is in effect, the grep utility will prefix each output line by: "%d:", <block number> o Finally, the following will be written to standard output: "%s", <selected-line contents> STDERR Used only for diagnostic messages. SEE ALSO ed(1), egrep(1), fgrep(1), regcomp(5), sed(1), sh(1) EXIT STATUS Exit status is 0 if any matches are found, 1 if none, >1 for syntax errors or inaccessible files (even if matches were found). CONSEQUENCES OF ERRORS If the -q option is specified, the exit status will be zero if an input line is selected, even if an error was detected. If the requested action cannot be performed on a file, grep will issue a diagnostic message to standard error and continue processing the next operand in sequence, but the final exit status is returned as non-zero. APPLICATION USAGE Care should be taken when using characters in pattern_list that may also be meaningful to the command interpreter. It is safest to enclose the entire pattern_list argument in single quotes: The -e pattern_list option has the same effect as the pattern_list operand, but is useful when pattern_list begins with the hyphen delimiter. It is also useful when it is more convenient to provide multiple patterns as separate arguments. Multiple -e and -f options are accepted and grep will use all of the patterns it is given while matching input text lines. (Note that the order of evaluation is not specified. If an implementation finds a null string as a pattern, it is allowed to use that pattern first, matching every line, and effectively ignore any other patterns.) The -q option provides a means of easily determining whether or not a pattern (or string) exists in a group of files. When searching several files, it provides a performance improvement (because it can quit as soon as it finds the first match) and requires less care by the user in choosing the set of files to supply as arguments (because it will exit zero if it finds a match even if grep detected an access or read error on earlier file operands). EXAMPLES 1. To find all uses of the word Posix in a bunch of files where some of the files cannot be opened due to permission restrictions: grep -q -n Posix /etc/* Note the above use of the -q command line option to grep. If the -q is not used in the above command line, then when the first file is encountered that is not readable grep will error terminate even if there were some matches found. 2. To find all uses of the word Posix (in any case) in file text.mm and write with line numbers: grep -i -n posix text.mm 3. To find all empty lines in the standard input: grep ^$ or: grep -v . 4. Both of the following commands print all lines containing strings abc or def or both: grep -E 'abc def' grep -F 'abc def' 5. Both of the following commands print all lines matching exactly abc or def: grep -E 'abc$ ^def$' grep -F -x 'abc def' BUGS If there is a line with embedded nulls, grep will only match up to the first null; if it matches, it will print the entire line. Page 5