32v 1m grep
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GREP(1) UNIX Programmer's Manual GREP(1)
grep, egrep, fgrep - search a file for a pattern
grep [ option ] ... expression [ file ] ...
egrep [ option ] ... [ expression ] [ file ] ...
fgrep [ option ] ... [ strings ] [ file ]
Commands of the _g_r_e_p family search the input _f_i_l_e_s (standard input default) for lines matching a pattern. Normally, each line found is copied to the standard output. _G_r_e_p patterns are limited regular expressions in the style of _e_d(1); it uses a compact nondeterministic algorithm. _E_g_r_e_p patterns are full regular expressions; it uses a fast deterministic algorithm that sometimes needs exponential space. _F_g_r_e_p patterns are fixed strings; it is fast and compact. The following options are recognized.
-v All lines but those matching are printed.
-x (Exact) only lines matched in their entirety are printed (_f_g_r_e_p only).
-c Only a count of matching lines is printed.
-l The names of files with matching lines are listed (once) separated by newlines.
-n Each line is preceded by its relative line number in the file.
-b Each line is preceded by the block number on which it was found. This is sometimes useful in locating disk block numbers by context.
-e _e_x_p_r_e_s_s_i_o_n Same as a simple _e_x_p_r_e_s_s_i_o_n argument, but useful when the _e_x_p_r_e_s_s_i_o_n begins with a -.
-f _f_i_l_e The regular expression (_e_g_r_e_p) or string list (_f_g_r_e_p) is taken from the _f_i_l_e.
In all cases the file name is shown if there is more than one input file. Care should be taken when using the charac- ters $ * [ ^ | ( ) and \ in the _e_x_p_r_e_s_s_i_o_n as they are also meaningful to the Shell. It is safest to enclose the entire _e_x_p_r_e_s_s_i_o_n argument in single quotes ' '.
_F_g_r_e_p searches for lines that contain one of the (newline- separated) _s_t_r_i_n_g_s.
_E_g_r_e_p accepts extended regular expressions. In the follow- ing description `character' excludes newline:
A \ followed by a single character other than newline matches that character.
The character ^ ($) matches the beginning (end) of a line.
A . matches any character.
A single character not otherwise endowed with special meaning matches that character.
A string enclosed in brackets  matches any single character from the string. Ranges of ASCII character codes may be abbreviated as in `a-z0-9'. A ] may occur only as the first character of the string. A literal - must be placed where it can't be mistaken as a range indicator.
A regular expression followed by * (+, ?) matches a sequence of 0 or more (1 or more, 0 or 1) matches of the regular expression.
Two regular expressions concatenated match a match of the first followed by a match of the second.
Two regular expressions separated by | or newline match either a match for the first or a match for the second.
A regular expression enclosed in parentheses matches a match for the regular expression.
The order of precedence of operators at the same parenthesis level is  then *+? then concatenation then | and newline.
Exit status is 0 if any matches are found, 1 if none, 2 for syntax errors or inaccessible files.
Ideally there should be only one _g_r_e_p, but we don't know a single algorithm that spans a wide enough range of space- time tradeoffs.
Lines are limited to 256 characters; longer lines are trun- cated.