Tcl_RegExpMatch(3tcl) Tcl Library Procedures Tcl_RegExpMatch(3tcl)
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NAME
Tcl_RegExpMatch, Tcl_RegExpCompile, Tcl_RegExpExec, Tcl_RegExpRange,
Tcl_GetRegExpFromObj, Tcl_RegExpMatchObj, Tcl_RegExpExecObj, Tcl_Reg-
ExpGetInfo - Pattern matching with regular expressions
SYNOPSIS
#include <tcl.h>
int
Tcl_RegExpMatchObj(interp, textObj, patObj)
int
Tcl_RegExpMatch(interp, text, pattern)
Tcl_RegExp
Tcl_RegExpCompile(interp, pattern)
int
Tcl_RegExpExec(interp, regexp, text, start)
void
Tcl_RegExpRange(regexp, index, startPtr, endPtr)
Tcl_RegExp
Tcl_GetRegExpFromObj(interp, patObj, cflags)
int
Tcl_RegExpExecObj(interp, regexp, textObj, offset, nmatches, eflags)
void
Tcl_RegExpGetInfo(regexp, infoPtr)
ARGUMENTS
Tcl_Interp *interp (in) Tcl interpreter to use for error
reporting. The interpreter may be
NULL if no error reporting is de-
sired.
Tcl_Obj *textObj (in/out) Refers to the value from which to
get the text to search. The in-
ternal representation of the value
may be converted to a form that
can be efficiently searched.
Tcl_Obj *patObj (in/out) Refers to the value from which to
get a regular expression. The com-
piled regular expression is cached
in the value.
const char *text (in) Text to search for a match with a
regular expression.
const char *pattern (in) String in the form of a regular
expression pattern.
Tcl_RegExp regexp (in) Compiled regular expression. Must
have been returned previously by
Tcl_GetRegExpFromObj or Tcl_RegEx-
pCompile.
const char *start (in) If text is just a portion of some
other string, this argument iden-
tifies the beginning of the larger
string. If it is not the same as
text, then no “^” matches will be
allowed.
int index (in) Specifies which range is desired:
0 means the range of the entire
match, 1 or greater means the
range that matched a parenthesized
sub-expression.
const char **startPtr (out) The address of the first character
in the range is stored here, or
NULL if there is no such range.
const char **endPtr (out) The address of the character just
after the last one in the range is
stored here, or NULL if there is
no such range.
int cflags (in) OR-ed combination of the compila-
tion flags TCL_REG_ADVANCED,
TCL_REG_EXTENDED, TCL_REG_BASIC,
TCL_REG_EXPANDED, TCL_REG_QUOTE,
TCL_REG_NOCASE, TCL_REG_NEWLINE,
TCL_REG_NLSTOP, TCL_REG_NLANCH,
TCL_REG_NOSUB, and TCL_REG_CAN-
MATCH. See below for more informa-
tion.
int offset (in) The character offset into the text
where matching should begin. The
value of the offset has no impact
on ^ matches. This behavior is
controlled by eflags.
int nmatches (in) The number of matching subexpres-
sions that should be remembered
for later use. If this value is
0, then no subexpression match in-
formation will be computed. If
the value is -1, then all of the
matching subexpressions will be
remembered. Any other value will
be taken as the maximum number of
subexpressions to remember.
int eflags (in) OR-ed combination of the execution
flags TCL_REG_NOTBOL and
TCL_REG_NOTEOL. See below for more
information.
Tcl_RegExpInfo *infoPtr (out) The address of the location where
information about a previous match
should be stored by Tcl_RegExpGet-
Info.
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DESCRIPTION
Tcl_RegExpMatch determines whether its pattern argument matches regexp,
where regexp is interpreted as a regular expression using the rules in
the re_syntax reference page. If there is a match then Tcl_RegExpMatch
returns 1. If there is no match then Tcl_RegExpMatch returns 0. If an
error occurs in the matching process (e.g. pattern is not a valid regu-
lar expression) then Tcl_RegExpMatch returns -1 and leaves an error
message in the interpreter result. Tcl_RegExpMatchObj is similar to
Tcl_RegExpMatch except it operates on the Tcl values textObj and patObj
instead of UTF strings. Tcl_RegExpMatchObj is generally more efficient
than Tcl_RegExpMatch, so it is the preferred interface.
Tcl_RegExpCompile, Tcl_RegExpExec, and Tcl_RegExpRange provide lower-
level access to the regular expression pattern matcher. Tcl_RegExpCom-
pile compiles a regular expression string into the internal form used
for efficient pattern matching. The return value is a token for this
compiled form, which can be used in subsequent calls to Tcl_RegExpExec
or Tcl_RegExpRange. If an error occurs while compiling the regular ex-
pression then Tcl_RegExpCompile returns NULL and leaves an error mes-
sage in the interpreter result. Note: the return value from Tcl_Reg-
ExpCompile is only valid up to the next call to Tcl_RegExpCompile; it
is not safe to retain these values for long periods of time.
Tcl_RegExpExec executes the regular expression pattern matcher. It re-
turns 1 if text contains a range of characters that match regexp, 0 if
no match is found, and -1 if an error occurs. In the case of an error,
Tcl_RegExpExec leaves an error message in the interpreter result. When
searching a string for multiple matches of a pattern, it is important
to distinguish between the start of the original string and the start
of the current search. For example, when searching for the second oc-
currence of a match, the text argument might point to the character
just after the first match; however, it is important for the pattern
matcher to know that this is not the start of the entire string, so
that it does not allow “^” atoms in the pattern to match. The start
argument provides this information by pointing to the start of the
overall string containing text. Start will be less than or equal to
text; if it is less than text then no ^ matches will be allowed.
Tcl_RegExpRange may be invoked after Tcl_RegExpExec returns; it pro-
vides detailed information about what ranges of the string matched what
parts of the pattern. Tcl_RegExpRange returns a pair of pointers in
*startPtr and *endPtr that identify a range of characters in the source
string for the most recent call to Tcl_RegExpExec. Index indicates
which of several ranges is desired: if index is 0, information is re-
turned about the overall range of characters that matched the entire
pattern; otherwise, information is returned about the range of charac-
ters that matched the index'th parenthesized subexpression within the
pattern. If there is no range corresponding to index then NULL is
stored in *startPtr and *endPtr.
Tcl_GetRegExpFromObj, Tcl_RegExpExecObj, and Tcl_RegExpGetInfo are
value interfaces that provide the most direct control of Henry
Spencer's regular expression library. For users that need to modify
compilation and execution options directly, it is recommended that you
use these interfaces instead of calling the internal regexp functions.
These interfaces handle the details of UTF to Unicode translations as
well as providing improved performance through caching in the pattern
and string values.
Tcl_GetRegExpFromObj attempts to return a compiled regular expression
from the patObj. If the value does not already contain a compiled reg-
ular expression it will attempt to create one from the string in the
value and assign it to the internal representation of the patObj. The
return value of this function is of type Tcl_RegExp. The return value
is a token for this compiled form, which can be used in subsequent
calls to Tcl_RegExpExecObj or Tcl_RegExpGetInfo. If an error occurs
while compiling the regular expression then Tcl_GetRegExpFromObj re-
turns NULL and leaves an error message in the interpreter result. The
regular expression token can be used as long as the internal represen-
tation of patObj refers to the compiled form. The cflags argument is a
bit-wise OR of zero or more of the following flags that control the
compilation of patObj:
TCL_REG_ADVANCED
Compile advanced regular expressions (“ARE”s). This mode cor-
responds to the normal regular expression syntax accepted by
the Tcl regexp and regsub commands.
TCL_REG_EXTENDED
Compile extended regular expressions (“ERE”s). This mode cor-
responds to the regular expression syntax recognized by Tcl
8.0 and earlier versions.
TCL_REG_BASIC
Compile basic regular expressions (“BRE”s). This mode corre-
sponds to the regular expression syntax recognized by common
Unix utilities like sed and grep. This is the default if no
flags are specified.
TCL_REG_EXPANDED
Compile the regular expression (basic, extended, or advanced)
using an expanded syntax that allows comments and whitespace.
This mode causes non-backslashed non-bracket-expression white
space and #-to-end-of-line comments to be ignored.
TCL_REG_QUOTE
Compile a literal string, with all characters treated as ordi-
nary characters.
TCL_REG_NOCASE
Compile for matching that ignores upper/lower case distinc-
tions.
TCL_REG_NEWLINE
Compile for newline-sensitive matching. By default, newline
is a completely ordinary character with no special meaning in
either regular expressions or strings. With this flag, “[^”
bracket expressions and “.” never match newline, “^” matches
an empty string after any newline in addition to its normal
function, and “$” matches an empty string before any newline
in addition to its normal function. REG_NEWLINE is the bit-
wise OR of REG_NLSTOP and REG_NLANCH.
TCL_REG_NLSTOP
Compile for partial newline-sensitive matching, with the be-
havior of “[^” bracket expressions and “.” affected, but not
the behavior of “^” and “$”. In this mode, “[^” bracket ex-
pressions and “.” never match newline.
TCL_REG_NLANCH
Compile for inverse partial newline-sensitive matching, with
the behavior of “^” and “$” (the “anchors”) affected, but not
the behavior of “[^” bracket expressions and “.”. In this
mode “^” matches an empty string after any newline in addition
to its normal function, and “$” matches an empty string before
any newline in addition to its normal function.
TCL_REG_NOSUB
Compile for matching that reports only success or failure, not
what was matched. This reduces compile overhead and may im-
prove performance. Subsequent calls to Tcl_RegExpGetInfo or
Tcl_RegExpRange will not report any match information.
TCL_REG_CANMATCH
Compile for matching that reports the potential to complete a
partial match given more text (see below).
Only one of TCL_REG_EXTENDED, TCL_REG_ADVANCED, TCL_REG_BASIC, and
TCL_REG_QUOTE may be specified.
Tcl_RegExpExecObj executes the regular expression pattern matcher. It
returns 1 if objPtr contains a range of characters that match regexp, 0
if no match is found, and -1 if an error occurs. In the case of an er-
ror, Tcl_RegExpExecObj leaves an error message in the interpreter re-
sult. The nmatches value indicates to the matcher how many subexpres-
sions are of interest. If nmatches is 0, then no subexpression match
information is recorded, which may allow the matcher to make various
optimizations. If the value is -1, then all of the subexpressions in
the pattern are remembered. If the value is a positive integer, then
only that number of subexpressions will be remembered. Matching begins
at the specified Unicode character index given by offset. Unlike
Tcl_RegExpExec, the behavior of anchors is not affected by the offset
value. Instead the behavior of the anchors is explicitly controlled by
the eflags argument, which is a bit-wise OR of zero or more of the fol-
lowing flags:
TCL_REG_NOTBOL
The starting character will not be treated as the beginning of
a line or the beginning of the string, so “^” will not match
there. Note that this flag has no effect on how “\A” matches.
TCL_REG_NOTEOL
The last character in the string will not be treated as the
end of a line or the end of the string, so “$” will not match
there. Note that this flag has no effect on how “\Z” matches.
Tcl_RegExpGetInfo retrieves information about the last match performed
with a given regular expression regexp. The infoPtr argument contains
a pointer to a structure that is defined as follows:
typedef struct Tcl_RegExpInfo {
int nsubs;
Tcl_RegExpIndices *matches;
long extendStart;
} Tcl_RegExpInfo;
The nsubs field contains a count of the number of parenthesized subex-
pressions within the regular expression. If the TCL_REG_NOSUB was
used, then this value will be zero. The matches field points to an ar-
ray of nsubs+1 values that indicate the bounds of each subexpression
matched. The first element in the array refers to the range matched by
the entire regular expression, and subsequent elements refer to the
parenthesized subexpressions in the order that they appear in the pat-
tern. Each element is a structure that is defined as follows:
typedef struct Tcl_RegExpIndices {
long start;
long end;
} Tcl_RegExpIndices;
The start and end values are Unicode character indices relative to the
offset location within objPtr where matching began. The start index
identifies the first character of the matched subexpression. The end
index identifies the first character after the matched subexpression.
If the subexpression matched the empty string, then start and end will
be equal. If the subexpression did not participate in the match, then
start and end will be set to -1.
The extendStart field in Tcl_RegExpInfo is only set if the TCL_REG_CAN-
MATCH flag was used. It indicates the first character in the string
where a match could occur. If a match was found, this will be the same
as the beginning of the current match. If no match was found, then it
indicates the earliest point at which a match might occur if additional
text is appended to the string. If it is no match is possible even
with further text, this field will be set to -1.
SEE ALSO
re_syntax(3tcl)
KEYWORDS
match, pattern, regular expression, string, subexpression, Tcl_RegEx-
pIndices, Tcl_RegExpInfo
Tcl 8.1 Tcl_RegExpMatch(3tcl)
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