REGCMP(3X-SysV) RISC/os Reference Manual REGCMP(3X-SysV)
NAME
regcmp, regex - compile and execute regular expression
SYNOPSIS
char *regcmp (string1 [, string2, ...], (char *)0)
char *string1, *string2, ...;
char *regex (re, subject[, ret0, ...])
char *re, *subject, *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 their associated mean-
ings.
[]*.^ 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
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.
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REGCMP(3X-SysV) RISC/os Reference Manual REGCMP(3X-SysV)
If only m is present (e.g., {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,
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.
They must, therefore, be escaped with a \ (backslash) to be
used as themselves.
EXAMPLES
Example 1:
char *cursor, *newcursor, *ptr;
...
newcursor = regex((ptr = regcmp("^\n", (char *)0)), cursor);
free(ptr);
This example will match a leading new-line in the subject
string pointed at by cursor.
Example 2:
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);
This example will match through the string ``Testing3'' and
will return the address of the character after the last
matched character (the ``4''). The string ``Testing3'' will
be copied to the character array ret0.
Example 3:
#include "file.i"
char *string, *newcursor;
...
newcursor = regex(name, string);
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REGCMP(3X-SysV) RISC/os Reference Manual REGCMP(3X-SysV)
This example applies a precompiled regular expression in
file.i [see regcmp(1)] against string.
These routines are kept in /lib/libPW.a.
SEE ALSO
malloc(3C).
ed(1), regcmp(1) in the User's Reference Manual.
ERRORS
The user program may run out of memory if regcmp is called
iteratively without freeing the vectors no longer required.
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