grep(C)

grep, egrep, fgrep -- search files for a pattern

Syntax

grep [ -E | -F ] [ -c | -l | -q ] [ -bhinsvxy ] [ -e expression ] [ -f expfile ]
[ expression ] [ file ... ]

egrep [ -c | -l | -q] [ -bhinsvxy ] [ -e expression ] [ -f expfile ] [ expression ]
[ file ... ]

fgrep [ -c | -l | -q ] [ -bhinsvxy ] [ -e expression ] [ -f expfile ] [ expression ]
[ file ... ]

Description

Commands of the grep family search the input files (or standard input if no file argument is specified) for lines matching a pattern. Normally, each matching line is copied to the standard output. If more than one file is being searched, the name of the file in which each match occurs is also written to the standard output along with the matching line (unless the -h option is used, see below).

The three grep commands differ significantly in use:

grep: Searches for fixed strings or basic regular expressions (patterns). grep regular expressions are described in regexp(M); see also Chapter 12, ``Regular expressions'' in the SCO OpenServer Operating System User's Guide for an introduction.
egrep: Searches for extended regular expressions (including expression groups, and alternatives). Note that the X/Open CAE Specification, Commands and Utilities, Issue 4, Version 2, 1994. marks this command as obsolescent: use the grep -E option instead.
fgrep: Searches for fixed strings. fgrep does not recognize regular expressions, but can find literal text rapidly. Note that the X/Open CAE Specification, Commands and Utilities, Issue 4, Version 2, 1994. marks this command as obsolescent: use the grep -F option instead.

grep and egrep also accept 3-digit octal character specifications in pattern strings of the form:

\0nnn

The octal form is replaced with the corresponding ASCII character (for example, ``\0101'' corresponds to ``A''). See ascii(M) for a list of characters and their octal equivalents.

The following options are recognized:

-E: Each pattern is treated as an extended regular expression. A null extended regular expression matches all lines. (The equivalent of egrep.)
-F: Each pattern is treated as a string instead of a regular expression. A null string matches all lines. (The equivalent of fgrep.)
-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.
-c: Only a count of matching lines is displayed.
-e expression: Specify patterns to be used during the search. The patterns in the list must be separated by a newline character. Multiple -e and -f options are accepted. Unless the -E or -F options are specified, grep treats the patterns as basic regular expressions.
-f expfile: The regular expression for grep, or extended expression for egrep, or strings list for fgrep is taken from the expfile. Patterns in the file are terminated by a newline character. Unless the -E or -F options are specified, grep treats the patterns as basic regular expressions.
-h: Prevents the name of the file containing the matching line from being printed before that line. Used when searching multiple files.
-i: Turns on matching of letters of either case in the input so that case is insignificant. Conversion between uppercase and lowercase letters is dependent on the locale setting.
-l: Only the names of files with matching lines are displayed, separated by newlines.
-n: Each line is preceded by its relative line number in the file.
-q: Quiet. Nothing is written to the standard output. grep exits with status 0 if an input line is selected. This provides a quick and easy method of testing if a pattern or string exists in a group of files.
-s: Suppresses error messages produced for nonexistent or unreadable files. Other error messages are not suppressed.
-v: All lines but those matching are displayed.
-x: Displays only exact matches of an entire line.

The following option is not a standard UNIX system option, and is maintained for backwards compatibility with XENIX:

-y: Turns on matching of letters of either case in the input so that case is insignificant. Conversion between uppercase and lowercase letters is dependent on the locale setting.

In all cases (except with -h) the filename is output if there is more than one input file. Care should be taken when using the characters $ [ ^ | ( ) and \ in expression, because they are also meaningful to the shell. It is safest to enclose the entire expression or strings argument in single quotation marks. For example:

grep '[Ss]omeone' text.file

This command would find all lines containing the word ``someone'' in the file text.file, whether the initial ``s'' is uppercase or lowercase.

Multiple strings can be specified without using a separate pattern file by using the quoting conventions of the shell to imbed newlines in the string argument. For example, if you were using the Bourne shell (see sh(C)) you might enter the following on the command line:

fgrep ´Someone

someone´ text.file

See the csh(C) manual page for ways to imbed newlines in a string when using csh.

grep -E (and egrep) accept regular expressions as in ed(C), with the following additions:

A regular expression followed by a plus sign (+) matches one or more occurrences of the regular expression.
A regular expression followed by a question mark (?) matches 0 or 1 occurrences of the regular expression.
Two regular expressions separated by a vertical bar (|) or by a newline match strings that are matched by either regular expression.
A regular expression may be enclosed in parentheses, (), for grouping. For example:

egrep ´([Ss]ome|[Aa]ny)one´ text.file
or

grep -E ´([Ss]ome|[Aa]ny)one´ text.file
This example displays all lines in text.file containing the words ``someone'' or ``anyone'', whether or not they are spelled with initial capital letters. Without the parentheses, this example would display all lines containing the words ``some'' or ``anyone'' (because the vertical bar (|) operator is of lower precedence than concatenation, see below).

The order of precedence of operators is [ ], then

? +, then concatenation, then backslash (\) with newline or vertical bar (|).

Exit values

Exit status is 0 if any matches are found, 1 if no matches are found, and 2 for syntax errors or inaccessible files.

Examples

To search the file /etc/passwd for all lines containing the name ``henry'':

grep -F henry /etc/passwd

To search /etc/passwd for lines containing the name ``henry'' in upper or lower case (or capitalized):

grep -F -i henry /etc/passwd

To search mytext for lines containing any mention of Henry, in any case and, optionally, with any suffix (for example, ``Henry's'', ``Henrys'''):

grep -i "henry[´s]*" mytext

To search mytext for lines containing ``Henry'' or ``Henrietta'':

grep -E '[Hh]enr(y|ietta)' mytext

(Note the shell quoting conventions in the above examples.)

Limitations

Lines are limited to {LINE_MAX} characters.

Open UNIX 8 compatibility notes

When running ACP on Open UNIX 8 and UnixWare 7 systems, set OSRCMDS=on to use the SCO OpenServer version of the <grep> commands. This provides the expected behaviors for SCO OpenServer applications. The SCO OpenServer version of this command is also provided on Open UNIX 8 systems under the OSP feature See the Running SCO OpenServer Applications topic in the Open UNIX 8 documentation set.

Standards conformance

egrep, fgrep and grep are conformant with:

ISO/IEC DIS 99452:1992, Information technology Portable Operating System Interface (POSIX) Part 2: Shell and Utilities (IEEE Std 1003.21992);
AT&T SVID Issue 2;
X/Open CAE Specification, Commands and Utilities, Issue 4, 1992;
X/Open CAE Specification, Commands and Utilities, Issue 4, Version 2, 1994.: note that egrep and fgrep are marked as obsolescent.