Provided by: tcl9.0-doc_9.0.1+dfsg-1_all 
NAME
Tcl_RegExpMatch, Tcl_RegExpCompile, Tcl_RegExpExec, Tcl_RegExpRange, Tcl_GetRegExpFromObj,
Tcl_RegExpMatchObj, Tcl_RegExpExecObj, Tcl_RegExpGetInfo - 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)
Tcl_RegExpRange(regexp, index, startPtr, endPtr)
Tcl_RegExp
Tcl_GetRegExpFromObj(interp, patObj, cflags)
int
Tcl_RegExpExecObj(interp, regexp, textObj, offset, nmatches, eflags)
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 desired.
Tcl_Obj *textObj (in/out) Refers to the value from which to get the text to search. The
internal 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
compiled 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_RegExpCompile.
const char *start (in) If text is just a portion of some other string, this argument
identifies the beginning of the larger string. If it is not the
same as text, then no “^” matches will be allowed.
Tcl_Size 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 compilation 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_CANMATCH. See below for more information.
Tcl_Size 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.
Tcl_Size nmatches (in) The number of matching subexpressions that should be remembered for
later use. If this value is 0, then no subexpression match
information will be computed. If the value is negative, 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_RegExpGetInfo.
________________________________________________________________________________________________________________
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 regular 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_RegExpCompile 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 expression then Tcl_RegExpCompile returns NULL and leaves an error message in the interpreter
result. Note that the return value from Tcl_RegExpCompile 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 returns 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 occurrence 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 provides 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
returned about the overall range of characters that matched the entire pattern; otherwise, information
is returned about the range of characters 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 regular 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 returns NULL and leaves an error message in the interpreter result.
The regular expression token can be used as long as the internal representation 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 corresponds 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 corresponds to the regular expression
syntax recognized by Tcl 8.0 and earlier versions.
TCL_REG_BASIC
Compile basic regular expressions (“BRE”s). This mode corresponds 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 ordinary characters.
TCL_REG_NOCASE
Compile for matching that ignores upper/lower case distinctions.
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 “$” matches an empty string before any newline in addition
to its normal function. REG_NEWLINE is the bit-wise OR of REG_NLSTOP and REG_NLANCH.
TCL_REG_NLSTOP
Compile for partial newline-sensitive matching, with the behavior of “[^” bracket expressions
and “.” affected, but not the behavior of “^” and “$”. In this mode, “[^” bracket expressions
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 improve 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 error, Tcl_RegExpExecObj leaves an error message in the interpreter result. The nmatches value
indicates to the matcher how many subexpressions 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 following 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_Size nsubs;
Tcl_RegExpIndices *matches;
Tcl_Size extendStart;
} Tcl_RegExpInfo;
The nsubs field contains a count of the number of parenthesized subexpressions within the regular
expression. If the TCL_REG_NOSUB was used, then this value will be zero. The matches field points to an
array 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 pattern. Each element is a structure
that is defined as follows:
typedef struct {
Tcl_Size start;
Tcl_Size 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_CANMATCH 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.
REFERENCE COUNT MANAGEMENT
The textObj and patObj arguments to Tcl_RegExpMatchObj must have reference counts of at least 1. Note
however that this function may set the interpreter result; neither argument should be the direct
interpreter result without an additional reference being taken.
The patObj argument to Tcl_GetRegExpFromObj must have a reference count of at least 1. Note however that
this function may set the interpreter result; the argument should not be the direct interpreter result
without an additional reference being taken.
The textObj argument to Tcl_RegExpExecObj must have a reference count of at least 1. Note however that
this function may set the interpreter result; the argument should not be the direct interpreter result
without an additional reference being taken.
SEE ALSO
re_syntax(3tcl)
KEYWORDS
match, pattern, regular expression, string, subexpression, Tcl_RegExpIndices, Tcl_RegExpInfo
Tcl 8.1 Tcl_RegExpMatch(3tcl)