Content-type: text/html Man page of regcmp

regcmp

Section: C Library Functions (3)
Index Return to Main Contents
 

NAME

regcmp, regex - Compile and execute regular expression  

LIBRARY

Standard C Library (libc.so, libc. a)  

SYNOPSIS

#include <libgen.h>

char *regcmp(        const char *string1,
       ... /*,
       (char *)0 */);

char *regex(        const char *re,
       const char *subject,
       ... );
 

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

regcmp(), regex():  XPG4-UNIX

Refer to the standards(5) reference page for more information about industry standards and associated tags.  

PARAMETERS

Points to the string that is to be matched or converted. Points to a compiled regular expression string. Points to the string that is to be matched against re.  

DESCRIPTION

The regcmp() function compiles a regular expression consisting of the concatenated arguments and returns a pointer to the compiled form. The end of arguments is indicated by a null pointer. The malloc() function is used to create space for the compiled form. It is the responsibility of the process to free unneeded space so allocated. A null pointer returned from regcmp() indicates an invalid argument.

The regex() function executes a compiled pattern against the subject string. Additional arguments of type char must be passed to receive matched subexpressions back. A global character pointer, __loc1, points to the first matched character in the subject string.

The regcmp() and regex() functions support the simple regular expressions which are defined in the grep(1) reference page, but the syntax and semantics are slightly different. The following are the valid symbols and their associated meanings: The left and right bracket, asterisk, period, and circumflex symbols retain their meanings as defined in the grep(1) reference page. A dollar sign matches the end of the string; \n matches a new line. Used within brackets, the hyphen signifies an ASCII character range. For example [a-z] is equivalent to [abcd...xyz]. The - (hyphen) can represent itself only if used as the first or last character. For example, the character class expression []-] matches the characters ] (right bracket) and - (hyphen). A regular expression followed by a + (plus sign) means one or more times. For example, [0-9]+ is equivalent to [0-9][0-9]*. Integer values enclosed in {} braces indicate the number of times the preceding regular expression can be applied. The value m is the minimum number and u is a number, less than 256, which is the maximum. The syntax {m} indicates the exact number of times the regular expression can be applied. The syntax {m,} is analogous to {m,infinity}. The + (plus sign) and * (asterisk) operations are equivalent to {1,} and {0,}, respectively. The value of the enclosed regular expression is returned. The value is stored in the (n+1)th argument following the subject argument. A maximum of ten enclosed regular expressions are allowed. The regex() function makes its assignments unconditionally. Parentheses are used for grouping. An operator, such as *, +, or {}, can work on a single character or a regular expression enclosed in parentheses. For example, (a*(cb+)*)$0.

Since all of the symbols defined above are special characters, they must be escaped to be used as themselves.  

NOTES

The regcmp() and regex() interfaces are scheduled to be withdrawn from a future version of the X/Open CAE Specification.

These interfaces are obsolete; they are guaranteed to function properly only in the C/POSIX locale and so should be avoided. Use the POSIX regcomp() interface instead of regcmp() and regex().  

RETURN VALUES

Upon successful completion, the regcmp() function returns a pointer to the compiled regular expression. Otherwise, a null pointer is returned and errno may be set to indicate the error.

Upon successful completion, the regex() function returns a pointer to the next unmatched character in the subject string. Otherwise, a null pointer is returned.  

RELATED INFORMATION

Commands: grep(1)

Functions: malloc(3), regcomp(3)

Standards: standards(5) delim off


 

Index

NAME
LIBRARY
SYNOPSIS
STANDARDS
PARAMETERS
DESCRIPTION
NOTES
RETURN VALUES
RELATED INFORMATION

This document was created by man2html, using the manual pages.
Time: 02:40:59 GMT, October 02, 2010