1GREP(1) General Commands Manual GREP(1)
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6 grep, egrep, fgrep - search a file for a pattern
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9 grep [ option ] ... expression [ file ] ...
10 egrep [ option ] ... [ expression ] [ file ] ...
12 fgrep [ option ] ... [ strings ] [ file ]
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16 Commands of the grep family search the input files (standard input
17 default) for lines matching a pattern. Normally, each line found is
18 copied to the standard output; unless the -h flag is used, the file
19 name is shown if there is more than one input file.
20 Grep patterns are limited regular expressions in the style of ed(1); it
22 uses a compact nondeterministic algorithm. Egrep patterns are full
23 regular expressions; it uses a fast deterministic algorithm that some‐
24 times needs exponential space. Fgrep patterns are fixed strings; it is
25 fast and compact.
26 The following options are recognized.
28 -v All lines but those matching are printed.
30 -c Only a count of matching lines is printed.
32 -l The names of files with matching lines are listed (once) sepa‐
34 rated by newlines.
35 -n Each line is preceded by its line number in the file.
37 -b Each line is preceded by the block number on which it was found.
39 This is sometimes useful in locating disk block numbers by con‐
40 text.
41 -s No output is produced, only status.
43 -h Do not print filename headers with output lines.
45 -y Lower case letters in the pattern will also match upper case
47 letters in the input (grep only).
48 -e expression
50 Same as a simple expression argument, but useful when the
51 expression begins with a -.
52 -f file
54 The regular expression (egrep) or string list (fgrep) is taken
55 from the file.
56 -x (Exact) only lines matched in their entirety are printed (fgrep
58 only).
59 Care should be taken when using the characters $ * [ ^ | ? ´ " ( ) and
61 \ in the expression as they are also meaningful to the Shell. It is
62 safest to enclose the entire expression argument in single quotes ´ ´.
63 Fgrep searches for lines that contain one of the (newline-separated)
65 strings.
66 Egrep accepts extended regular expressions. In the following descrip‐
68 tion `character' excludes newline:
69 A \ followed by a single character matches that character.
71 The character ^ ($) matches the beginning (end) of a line.
73 A . matches any character.
75 A single character not otherwise endowed with special meaning
77 matches that character.
78 A string enclosed in brackets [] matches any single character
80 from the string. Ranges of ASCII character codes may be abbre‐
81 viated as in `a-z0-9'. A ] may occur only as the first charac‐
82 ter of the string. A literal - must be placed where it can't be
83 mistaken as a range indicator.
84 A regular expression followed by * (+, ?) matches a sequence of
86 0 or more (1 or more, 0 or 1) matches of the regular expression.
87 Two regular expressions concatenated match a match of the first
89 followed by a match of the second.
90 Two regular expressions separated by | or newline match either a
92 match for the first or a match for the second.
93 A regular expression enclosed in parentheses matches a match for
95 the regular expression.
96 The order of precedence of operators at the same parenthesis level is
98 [] then *+? then concatenation then | and newline.
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101 ed(1), sed(1), sh(1)
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104 Exit status is 0 if any matches are found, 1 if none, 2 for syntax
105 errors or inaccessible files.
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108 Ideally there should be only one grep, but we don't know a single algo‐
109 rithm that spans a wide enough range of space-time tradeoffs.
110 Lines are limited to 256 characters; longer lines are truncated.
112 GREP(1)