Index of Section 3 Manual Pages
| Interix / SUA | Tcl_Merge.3 | Interix / SUA |
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)
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NAME
Tcl_SplitList, Tcl_Merge, Tcl_ScanElement, Tcl_ConvertEle-
ment, Tcl_ScanCountedElement, Tcl_ConvertCountedElement -
manipulate Tcl lists
SYNOPSIS
#include
int
Tcl_SplitList(interp, list, argcPtr, argvPtr)
char *
Tcl_Merge(argc, argv)
int
Tcl_ScanElement(src, flagsPtr)
int
Tcl_ScanCountedElement(src, length, flagsPtr)
int
Tcl_ConvertElement(src, dst, flags)
int
Tcl_ConvertCountedElement(src, length, dst, flags)
ARGUMENTS
Tcl_Interp *interp (out) Interpreter to
use for error
reporting. If
NULL, then no
error message
is left.
char *list (in) Pointer to a
string with
proper list
structure.
int *argcPtr (out) Filled in with
number of ele-
ments in list.
CONST char ***argvPtr (out) *argvPtr will
be filled in
with the
address of an
array of
pointers to
the strings
that are the
extracted ele-
ments of list.
There will be
*argcPtr valid
entries in the
array, fol-
lowed by a
NULL entry.
int argc (in) Number of ele-
ments in argv.
CONST char * CONST *argv (in) Array of
strings to
merge together
into a single
list. Each
string will
become a sepa-
rate element
of the list.
CONST char *src (in) String that is
to become an
element of a
list.
int *flagsPtr (in) Pointer to
word to fill
in with infor-
mation about
src. The
value of
*flagsPtr must
be passed to
Tcl_Con-
vertElement.
int length (in) Number of
bytes in
string src.
char *dst (in) Place to copy
converted list
element. Must
contain enough
characters to
hold converted
string.
int flags (in) Information
about src.
Must be value
returned by
previous call
to
Tcl_ScanEle-
ment, possibly
OR-ed with
TCL_DONT_USE_BRACES.
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DESCRIPTION
These procedures may be used to disassemble and reassemble
Tcl lists. Tcl_SplitList breaks a list up into its con-
stituent elements, returning an array of pointers to the
elements using argcPtr and argvPtr. While extracting the
arguments, Tcl_SplitList obeys the usual rules for back-
slash substitutions and braces. The area of memory
pointed to by *argvPtr is dynamically allocated; in addi-
tion to the array of pointers, it also holds copies of all
the list elements. It is the caller's responsibility to
free up all of this storage. For example, suppose that
you have called Tcl_SplitList with the following code:
int argc, code;
char *string;
char **argv;
...
code = Tcl_SplitList(interp, string, &argc, &argv);
Then you should eventually free the storage with a call
like the following:
Tcl_Free((char *) argv);
Tcl_SplitList normally returns TCL_OK, which means the
list was successfully parsed. If there was a syntax error
in list, then TCL_ERROR is returned and the interpreter's
result will point to an error message describing the prob-
lem (if interp was not NULL). If TCL_ERROR is returned
then no memory is allocated and *argvPtr is not modified.
Tcl_Merge is the inverse of Tcl_SplitList: it takes a
collection of strings given by argc and argv and generates
a result string that has proper list structure. This
means that commands like index may be used to extract the
original elements again. In addition, if the result of
Tcl_Merge is passed to Tcl_Eval, it will be parsed into
argc words whose values will be the same as the argv
strings passed to Tcl_Merge. Tcl_Merge will modify the
list elements with braces and/or backslashes in order to
produce proper Tcl list structure. The result string is
dynamically allocated using Tcl_Alloc; the caller must
eventually release the space using Tcl_Free.
If the result of Tcl_Merge is passed to Tcl_SplitList, the
elements returned by Tcl_SplitList will be identical to
those passed into Tcl_Merge. However, the converse is not
true: if Tcl_SplitList is passed a given string, and the
resulting argc and argv are passed to Tcl_Merge, the
resulting string may not be the same as the original
string passed to Tcl_SplitList. This is because Tcl_Merge
may use backslashes and braces differently than the origi-
nal string.
Tcl_ScanElement and Tcl_ConvertElement are the procedures
that do all of the real work of Tcl_Merge. Tcl_ScanEle-
ment scans its src argument and determines how to use
backslashes and braces when converting it to a list ele-
ment. It returns an overestimate of the number of charac-
ters required to represent src as a list element, and it
stores information in *flagsPtr that is needed by Tcl_Con-
vertElement.
Tcl_ConvertElement is a companion procedure to
Tcl_ScanElement. It does the actual work of converting a
string to a list element. Its flags argument must be the
same as the value returned by Tcl_ScanElement. Tcl_Con-
vertElement writes a proper list element to memory start-
ing at *dst and returns a count of the total number of
characters written, which will be no more than the result
returned by Tcl_ScanElement. Tcl_ConvertElement writes
out only the actual list element without any leading or
trailing spaces: it is up to the caller to include spaces
between adjacent list elements.
Tcl_ConvertElement uses one of two different approaches to
handle the special characters in src. Wherever possible,
it handles special characters by surrounding the string
with braces. This produces clean-looking output, but
can't be used in some situations, such as when src con-
tains unmatched braces. In these situations,
Tcl_ConvertElement handles special characters by generat-
ing backslash sequences for them. The caller may insist
on the second approach by OR-ing the flag value returned
by Tcl_ScanElement with TCL_DONT_USE_BRACES. Although
this will produce an uglier result, it is useful in some
special situations, such as when Tcl_ConvertElement is
being used to generate a portion of an argument for a Tcl
command. In this case, surrounding src with curly braces
would cause the command not to be parsed correctly.
Tcl_ScanCountedElement and Tcl_ConvertCountedElement are
the same as Tcl_ScanElement and Tcl_ConvertElement, except
the length of string src is specified by the length argu-
ment, and the string may contain embedded nulls.
KEYWORDS
backslash, convert, element, list, merge, split, strings
Tcl 8.0 Tcl_SplitList(3)