regcmp(3G)                                                       regcmp(3G)

NAME
     regcmp, regex - compile and execute regular expression

SYNOPSIS
     cc [flag ...] file ... -lgen [library ...]

     #include <libgen.h>

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

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

     extern char *loc1;

DESCRIPTION
     regcmp() compiles a regular expression consisting of the concatenated
     arguments, and returns a pointer to the compiled form. malloc(3C) is
     used to create memory space for the compiled form. It is the user's
     responsibility to free unneeded space so allocated. A NULL return from
     regcmp() indicates an incorrect argument.

     regex() searches for a compiled pattern against the subject string.
     Additional arguments are passed in order to receive values back.
     regex() returns NULL on failure or a pointer to the next unmatched
     character on success. A global character pointer loc1 points to
     where the match began. regcmp() and regex() were mostly borrowed from
     the editor, ed(1); however, the syntax and semantics have been changed
     slightly. The following are the valid symbols and associated meanings:

     []*.^ These symbols retain their meaning in ed(1).

     $     Matches the end of the string; the character sequence \n within
           a string, matches a newline.

     -     Within brackets the minus means through. For example, [az] is
           equivalent to [abcd...xyz]. The - can appear as itself only if
           used as the first or last character. For example, the character
           class expression []-] matches the characters ] and -.

     +     A regular expression followed by + means one or more times. For
           example, [0-9]+ is equivalent to [0-9][0-9]*.

     {m} {m,} {m,u}
           Integer values enclosed in {} indicate the number of times the
           preceding regular expression is to be applied. The value m is
           the minimum number and u is a number, less than 256, which is
           the maximum. If only m is present (i.e., {m}), it indicates the
           exact number of times the regular expression is to be applied.
           The value {m,} is analogous to {m,infinity}. The plus + and star
           * operations are equivalent to {1,} and {0,} respectively.





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regcmp(3G)                                                       regcmp(3G)

     ( ... )$n
           The value of the enclosed regular expression is to be returned.
           The value will be stored in the (n+1)th argument following the
           subject argument. At most, ten enclosed regular expressions are
           allowed. regex() makes its assignments unconditionally.

     ( ... )
           Parentheses are used for grouping. An operator, e.g., *, +, {},
           can work on a single character or a regular expression enclosed
           in parentheses. For example, (a*(cb+)*)$0.

     By necessity, all the above defined symbols are special characters.
     They must, therefore, be escaped with a backslash \ to be used as
     themselves.

EXAMPLES
     The following example matches a leading newline in the subject string
     pointed at by cursor.

        char *cursor, *newcursor, *ptr;
         ...
        newcursor = regex((ptr = regcmp("^\n", (char *)0)), cursor);
        free(ptr);

     The following example matches through the string Testing3 and returns
     the address of the character after the last matched character (the
     character 4). The string Testing3 is copied to the character array
     ret0.

        char ret0[9];
        char *newcursor, *name;
         ...
        name = regcmp("([A-Za-z][A-za-z0-9]{0,7})$0", (char *)0);
        newcursor = regex(name, "012Testing345", ret0);

     The following example applies a precompiled regular expression in
     file.i [see regcmp(1)] against string.

        #include "file.i"
        char *string, *newcursor;
         ...
        newcursor = regex(name, string);

ERRORS
     The regcmp() function may fail if:

     ENOMEM    Insufficient storage space was available.







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regcmp(3G)                                                       regcmp(3G)

NOTES
     The user program may be unable to provide any more memory if regcmp()
     is called iteratively without freeing the vectors no longer required.

     If you use one of these functions, you must link the libgen library at
     compilation (cc -lgen).

SEE ALSO
     ed(1), regcmp(1), regex(3), malloc(3C), regcomp(3C), regexpr(3G),
     expressions(5), libgen(5), recomp(5), regex(5), regexp(5).












































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