GREP(1) USER COMMANDS GREP(1) NAME grep, egrep - print lines matching a regular expression SYNOPSIS grep [ -CVbchilnsvwx ] [ -_n_u_m ] [ -AB _n_u_m ] [ [ -e ] _e_x_p_r | -f _f_i_l_e ] [ _f_i_l_e_s ... ] DESCRIPTION _G_r_e_p searches the files listed in the arguments (or standard input if no files are given) for all lines that contain a match for the given _e_x_p_r. If any lines match, they are printed. Also, if any matches were found, _g_r_e_p will exit with a status of 0, but if no matches were found it will exit with a status of 1. This is useful for building shell scripts that use _g_r_e_p as a condition for, for example, the _i_f state- ment. When invoked as _e_g_r_e_p the syntax of the _e_x_p_r is slightly different; See below. REGULAR EXPRESSIONS (grep) (egrep) (explanation) _c _c a single (non-meta) character matches itself. . . matches any single character except newline. \? ? postfix operator; preceeding item is optional. * * postfix operator; preceeding item 0 or more times. \+ + postfix operator; preceeding item 1 or more times. \| | infix operator; matches either argument. ^ ^ matches the empty string at the beginning of a line. $ $ matches the empty string at the end of a line. \< \< matches the empty string at the beginning of a word. GNU Project Last change: 1988 December 13 1 GREP(1) USER COMMANDS GREP(1) \> \> matches the empty string at the end of a word. [_c_h_a_r_s] [_c_h_a_r_s] match any character in the given class; if the first character after [ is ^, match any character not in the given class; a range of charac- ters may be specified by _f_i_r_s_t-_l_a_s_t; for example, \W (below) is equivalent to the class [^A-Za-z0-9] \( \) ( ) parentheses are used to override operator precedence. \_d_i_g_i_t \_d_i_g_i_t \_n matches a repeat of the text matched earlier in the regexp by the subexpression inside the nth opening parenthesis. \ \ any special character may be pre- ceded by a backslash to match it literally. (the following are for compatibility with GNU Emacs) \b \b matches the empty string at the edge of a word. \B \B matches the empty string if not at the edge of a word. \w \w matches word-constituent characters (letters & digits). \W \W matches characters that are not word-constituent. Operator precedence is (highest to lowest) ?, *, and +, con- catenation, and finally |. All other constructs are syntac- tically identical to normal characters. For the truly interested, the file dfa.c describes (and implements) the exact grammar understood by the parser. OPTIONS -A _n_u_m print lines of context after every matching line -B _n_u_m print _n_u_m lines of context before every matching line -C print 2 lines of context on each side of every match GNU Project Last change: 1988 December 13 2 GREP(1) USER COMMANDS GREP(1) -_n_u_m print _n_u_m lines of context on each side of every match -V print the version number on the diagnostic output -b print every match preceded by its byte offset -c print a total count of matching lines only -e _e_x_p_r search for _e_x_p_r; useful if _e_x_p_r begins with - -f _f_i_l_e search for the expression contained in _f_i_l_e -h don't display filenames on matches -i ignore case difference when comparing strings -l list files containing matches only -n print each match preceded by its line number -s run silently producing no output except error messages -v print only lines that contain no matches for the -w print only lines where the match is a complete word -x print only lines where the match is a whole line SEE ALSO emacs(1), ed(1), sh(1), _G_N_U _E_m_a_c_s _M_a_n_u_a_l INCOMPATIBILITIES The following incompatibilities with UNIX _g_r_e_p exist: The context-dependent meaning of * is not quite the same (grep only). -b prints a byte offset instead of a block offset. The {_m,_n} construct of System V grep is not imple- mented. BUGS GNU _e?_g_r_e_p has been thoroughly debugged and tested by several people over a period of several months; we think it's a reliable beast or we wouldn't distribute it. If by some fluke of the universe you discover a bug, send a detailed description (including options, regular expres- sions, and a copy of an input file that can reproduce it) to me, mike@wheaties.ai.mit.edu. GNU Project Last change: 1988 December 13 3 GREP(1) USER COMMANDS GREP(1) There is also a newsgroup, gnu.utils.bug, for reporting FSF utility programs' bugs and fixes; but before reporting some- thing as a bug, please try to be sure that it really is a bug, not a misunderstanding or a deliberate feature. Also, include the version number of the utility program you are running in _e_v_e_r_y bug report that you send in. Please do not send anything but bug reports to this newsgroup. AVAILABILITY GNU _g_r_e_p is free; anyone may redistribute copies of _g_r_e_p to anyone under the terms stated in the GNU General Public License, a copy of which may be found in each copy of _G_N_U _E_m_a_c_s. See also the comment at the beginning of the source code file grep.c. Copies of GNU _g_r_e_p may sometimes be received packaged with distributions of Unix systems, but it is never included in the scope of any license covering those systems. Such inclusion violates the terms on which distribution is per- mitted. In fact, the primary purpose of the General Public License is to prohibit anyone from attaching any other res- trictions to redistribution of any of the Free Software Foundation programs. AUTHORS Mike Haertel wrote the deterministic regexp code and the bulk of the program. James A. Woods is responsible for the hybridized search strategy of using Boyer-Moore-Gosper fixed-string search as a filter before calling the general regexp matcher. Arthur David Olson contributed code that finds fixed strings for the aforementioned BMG search for a large class of regexps. Richard Stallman wrote the backtracking regexp matcher that is used for \fIdigit backreferences, as well as the getopt that is provided for 4.2BSD sites. The backtracking matcher was originally written for GNU Emacs. D. A. Gwyn wrote the C alloca emulation that is provided so System V machines can run this program. (Alloca is used only by RMS' backtracking matcher, and then only rarely, so there is no loss if your machine doesn't have a "real" alloca.) Scott Anderson and Henry Spencer designed the regression tests used in the "regress" script. Paul Placeway wrote the original version of this manual page. GNU Project Last change: 1988 December 13 4