regcmp(3G)

Synopsis

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

   #include <libgen.h>
   

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

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

   extern char _ _loc1;

Description

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 newline.

-

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 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 (that is, {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.

( ... )$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, for example, , +, {}, 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. They must, therefore, be escaped with a \ (backslash) to be used as themselves.

Examples

   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 expression in file.i [see regcmp(1)] against string.

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

References

Notices