NAME

regcmp, regex − compile and execute regular expression

SYNOPSIS

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

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

extern char ∗loc1;

DESCRIPTION

Regcmp compiles a regular expression and returns a pointer to the compiled form.  Malloc(3C) is used to create space for the vector. 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 their associated meanings.

[]*.^ These symbols retain their current meaning. 

$ Matches the end of the string, \n matches the 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 last or first 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.  m is the minimum number and u is a number, less than 256, which is the maximum.  If only m is present (e.g., {m}), it indicates the exact number of times the regular expression is to be applied.  {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 present, 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 parenthesis.  For example, (a∗(cb+)∗)$0. 

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

EXAMPLE

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

matches a leading new-line in the subject string pointed at by cursor. 

char ret0[9];
char ∗newcursor, ∗name;
...
name = regcmp("([A−Za−z][A−za−z0−9_]{0,7})$0", 0);
newcursor = regex(name, "123Testing321", ret0);

matches through the string “Testing3” and will return the address of the character after the last matched character (cursor+11).  The string “Testing3” will be copied to the character array ret0.

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

applies a precompiled regular expression in file.i (see regcmp(1)) against string.

This routine is kept in /lib/libPW.a. 

SEE ALSO

ed(1), regcmp(1), malloc(3C). 

Version 2.3  —  July 04, 1985