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man pages section 1: User Commands

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Updated: Wednesday, February 9, 2022



egrep - search a file for a pattern using full regular expressions


/usr/bin/egrep [-bchilnsv] -e pattern_list [file...]
/usr/bin/egrep [-bchilnsv] -f file [file...]
/usr/bin/egrep [-bchilnsv] pattern [file...]
/usr/xpg4/bin/egrep [-bchilnqsvx] -e pattern_list [-f file] 
/usr/xpg4/bin/egrep [-bchilnqsvx] [-e pattern_list] -f file 
/usr/xpg4/bin/egrep [-bchilnqsvx] pattern [file...]


The egrep (expression grep) utility searches files for a pattern of characters and prints all lines that contain that pattern. egrep uses full regular expressions (expressions that have string values that use the full set of alphanumeric and special characters) to match the patterns. It uses a fast deterministic algorithm that sometimes needs exponential space.

If no files are specified, egrep assumes standard input. Normally, each line found is copied to the standard output. The file name is printed before each line found if there is more than one input file.


The /usr/bin/egrep utility accepts full regular expressions as described on the regexp(7) manual page, except for \( and \), \( and \), \{ and \}, \< and \>, and \n, and with the addition of:

  1. A full regular expression followed by + that matches one or more occurrences of the full regular expression.

  2. A full regular expression followed by ? that matches 0 or 1 occurrences of the full regular expression.

  3. Full regular expressions separated by | or by a NEWLINE that match strings that are matched by any of the expressions.

  4. A full regular expression that can be enclosed in parentheses ()for grouping.

Be careful using the characters $, *, [, ^, |, (, ), and \ in full regular expression, because they are also meaningful to the shell. It is safest to enclose the entire full regular expression in single quotes (´´).

The order of precedence of operators is [ ], then * ? +, then concatenation, then | and NEWLINE.


The /usr/xpg4/bin/egrep utility uses the regular expressions described in the EXTENDED REGULAR EXPRESSIONS section of the regex(7) manual page.


The following options are supported for both /usr/bin/egrep and /usr/xpg4/bin/egrep:


Precede each line by the block number on which it was found. This can be useful in locating block numbers by context (first block is 0).


Print only a count of the lines that contain the pattern.

–e pattern_list

Search for a pattern_list (full regular expression that begins with a ).

–f file

Take the list of full regular expressions from file.


Suppress printing of filenames when searching multiple files.


Ignore upper/lower case distinction during comparisons.


Print the names of files with matching lines once, separated by NEWLINEs. Does not repeat the names of files when the pattern is found more than once.


Precede each line by its line number in the file (first line is 1).


Work silently, that is, display nothing except error messages. This is useful for checking the error status.


Print all lines except those that contain the pattern.


The following options are supported for /usr/xpg4/bin/egrep only:


Quiet. Does not write anything to the standard output, regardless of matching lines. Exits with zero status if an input line is selected.


Consider only input lines that use all characters in the line to match an entire fixed string or regular expression to be matching lines.


The following operands are supported:


A path name of a file to be searched for the patterns. If no file operands are specified, the standard input is used.



Specify a pattern to be used during the search for input.



Specify one or more patterns to be used during the search for input. This operand is treated as if it were specified as –epattern_list..

Environment Variables

See environ(7) for descriptions of the following environment variables that affect the execution of egrep: LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH.

Exit Status

The following exit values are returned:


If any matches are found.


If no matches are found.


For syntax errors or inaccessible files (even if matches were found).


See attributes(7) for descriptions of the following attributes:


Not Enabled



See Also

fgrep(1), grep(1), sed(1), sh(1), XPG4(7), attributes(7), environ(7), regex(7), regexp(7)


Ideally there should be only one grep command, but there is not a single algorithm that spans a wide enough range of space-time trade-offs.

Lines are limited only by the size of the available virtual memory.


The /usr/xpg4/bin/egrep utility is identical to /usr/xpg4/bin/grep –E. See grep(1). Portable applications should use /usr/xpg4/bin/grep –E.