NAME

egrep - search a file for a pattern

SYNOPSIS

egrep [ option ] ...  [ expression ] [ file ] ... 

DESCRIPTION

Commands of the grep family search the input files (standard input default) for lines matching a pattern.  Normally, each line found is copied to the standard output.  Egrep patterns are full regular expressions; it uses a fast deterministic algorithm that sometimes needs exponential space.  The following options are recognized. 

−v All lines but those matching are printed. 

−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. 

−s Silent mode.  Nothing is printed (except error messages).  This is useful for checking the error status. 

−e expression
Same as a simple expression argument, but useful when the expression begins with a −. 

−f file The regular expression is taken from the named file which contains a list of regular expressions to be matched.  Each regular expression should appear on a separate line. 

The file names are shown in the output if more than one file was searched. 

Care should be taken when using the characters $ * [ ^ | ( ) and \ in the expression as they are also meaningful to the Shell.  It is safest to enclose the entire expression argument in single or double quotes ´ ´.  Use double quotes

Egrep accepts regular expressions and it also can accept patterns with "metacharacters".  The metacharacter matching protocol is as follows: (note that newline is not considered to be a ’character’). 

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.

EXAMPLE

egrep ’^This | match* | regular | expression$’ file1 file2 file3

will cause all the lines in the three files to be printed that match any of the expressions indicated. 

SEE ALSO

ex(1), fgrep(1), grep(1), sed(1), sh(1)

DIAGNOSTICS

Exit status is 0 if any matches are found, 1 if none, 2 for syntax errors or inaccessible files. 

BUGS

Ideally there should be only one grep, 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 truncated. 

7th Edition  —  1/7/82