REGCMP(3G-SVR4)     RISC/os Reference Manual      REGCMP(3G-SVR4)



NAME
     regcmp, regex - compile and execute regular expression

SYNOPSIS
     #include <libgen.h>

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

     char *regcmp (const char *string1 [, char *string2, ...],
         (char *)0);

     char *regex (const char *re, const char *subject
         [, char *ret0, ...]);

     extern char *__loc1;

DESCRIPTION
     regcmp compiles a regular expression (consisting of the con-
     catenated arguments) and returns a pointer to the compiled
     form.  malloc(3C) is used to create 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.  regcmp(1) has been written to generally
     preclude the need for this routine at execution time.

     regex executes a compiled pattern against the subject
     string.  Additional arguments are passed 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; \n matches a new-
               line.

     -         Within brackets the minus means through.  For
               example, [a-z] 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



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               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 (*) opera-
               tions are equivalent to {1,} and {0,} respec-
               tively.

     ( ... )$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 uncondition-
               ally.

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

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

EXAMPLES
     The following example matches a leading newline in the sub-
     ject 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 ``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 expres-
     sion in file.i [see regcmp(1)] against string.

          #include "file.i"
          char *string, *newcursor;
               ...



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REGCMP(3G-SVR4)     RISC/os Reference Manual      REGCMP(3G-SVR4)



          newcursor = regex(name, string);

SEE ALSO
     regcmp(1), malloc(3C).
     ed(1) in the User's Reference Manual.

NOTES
     The user program may run out of memory if regcmp is called
     iteratively without freeing the vectors no longer required.














































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