regexp(3X) regexp(3X)
NAME
compile(), step(), advance() - regular expression compile and match routines
SYNOPSIS
Remarks
Features documented in this manual entry are obsolescent and may be removed in a future HP-UX release. Use of regcomp(3C) functions
instead is recommended.
DESCRIPTION
These functions are general-purpose regular expression matching routines to be used in programs that perform Basic Regular Expression (see
regexp(5)) matching. These functions are defined in
The functions and do pattern matching given a character string and a compiled regular expression as input. takes a Basic Regular Expres-
sion as input and produces a compiled expression that can be used with and
The interface to this file is unpleasantly complex. Programs that include this file must have the following five macros declared before
the statement. These macros are used by the routine.
Return the value of the next byte
in the regular expression pattern. Successive calls to should return successive bytes of the regular expression.
Return the next byte in the regular
expression. Successive calls to should return the same byte (which should also be the next byte returned by
Cause the argument
c to be returned by the next call to (and No more than one byte of pushback is ever needed, and this byte is guaranteed to
be the last byte read by The value of the macro is always ignored.
This macro is used on normal exit of the
routine. The value of the argument pointer is a pointer to the character after the last character of the compiled regular
expression. This is useful to programs that must manage memory allocation.
This is the abnormal return from the
routine. The argument val is an error number (see table below for meanings). This call should never return.
11 Range endpoint too large.
16 Bad number.
25 ``digit'' out of range.
36 Illegal or missing delimiter.
41 No remembered search string.
42 imbalance.
43 Too many
44 More than 2 numbers given in
45 expected after
46 First number exceeds second in
49 imbalance.
50 Regular expression overflow.
The syntax of the routine is as follows:
The first parameter instring is never used explicitly by the routine, but is useful for programs that pass down different pointers to input
characters. It is sometimes used in the declaration (see below). Programs that call functions to input characters or have characters in
an external array can pass down a value of for this parameter.
The next parameter expbuf is a character pointer. It points to the location where the compiled regular expression will be placed.
The parameter endbuf is one more than the highest address where the compiled regular expression can be placed. If the compiled expression
cannot fit in (endbuf-expbuf) bytes, a call to is made.
The parameter eof is the character which marks the end of the regular expression. For example, in ed(1), this character is usually a
Each program that includes this file must have a statement for This definition is placed right after the declaration for the function and
the opening curly brace It is used for dependent declarations and initializations. Most often it is used to set a register variable to
point to the beginning of the regular expression so that this register variable can be used in the declarations for and Otherwise it can be
used to declare external variables that might be used by and See the example below of the declarations taken from grep(1).
also performs actual regular expression matching in this file. The call to step is as follows:
The first parameter to is a pointer to a string of characters to be checked for a match. This string should be null-terminated.
The second parameter expbuf is the compiled regular expression that was obtained by a call to
returns non-zero if the given string matches the regular expression, and zero if the expressions do not match. If there is a match, two
external character pointers are set as a side effect to the call to The variable set in is This is a pointer to the first character that
matched the regular expression. The variable which is set by the function points to the character after the last character that matches
the regular expression. Thus, if the regular expression matches the entire line, points to the first character of string and points to the
null at the end of string.
uses the external variable which is set by if the regular expression begins with If this is set, tries to match the regular expression to
the beginning of the string only. If more than one regular expression is to be compiled before the first is executed, the value of circf
should be saved for each compiled expression and circf should be set to that saved value before each call to
is called from with the same arguments as The purpose of is to step through the string argument and call until returns non-zero, which
indicates a match, or until the end of string is reached. To constrain string to beginning-of-line in all cases, need not be called; sim-
ply call
When encounters a or sequence in the regular expression, it advances its pointer to the string to be matched as far as possible and recur-
sively calls itself, trying to match the rest of the string to the rest of the regular expression. As long as there is no match, advance
backs up along the string until it finds a match or reaches the point in the string that initially matched the or It is sometimes desirable
to stop this backing up before the initial point in the string is reached. If the external character pointer is equal to the point in the
string at sometime during the backing up process, breaks out of the loop that backs up and returns zero. This is used by ed(1) and sed(1)
for substitutions done globally (not just the first occurrence, but the whole line) so, for example, expressions such as do not loop for-
ever.
The additional external variables and are used for special purposes.
EXTERNAL INFLUENCES
Locale
The category determines the collating sequence used in compiling and executing regular expressions.
The category determines the interpretation of text as single and/or multi-byte characters, and the characters matched by character class
expressions in regular expressions.
International Code Set Support
Single- and multi-byte character code sets are supported.
EXAMPLES
The following is an example of how the regular expression macros and calls look from grep(1):
...
...
SEE ALSO
grep(1), regcomp(3C), setlocale(3C), regexp(5).
STANDARDS CONFORMANCE
regexp(3X)