Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)_________________________________________________________________NAME
Tcl_SplitList, Tcl_Merge, Tcl_ScanElement, Tcl_ConvertEle-
ment - manipulate Tcl lists
SYNOPSIS
#include <tcl.h>
int
Tcl_SplitList(interp, list, argcPtr, argvPtr)
char *
Tcl_Merge(argc, argv)
int
Tcl_ScanElement(src, flagsPtr)
int
Tcl_ConvertElement(src, 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 elements in list.
char ***argvPtr (out) *argvPtr will be
filled in with the
address of an array of
pointers to the
strings that are the
extracted elements of
list. There will be
*argcPtr valid entries
in the array, followed
by a NULL entry.
int argc (in) Number of elements in
argv.
char **argv (in) Array of strings to
merge together into a
single list. Each
string will become a
separate element of
the list.
Tcl 7.5 1
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)
char *src (in) String that is to
become an element of a
list.
int *flagsPtr (in) Pointer to word to
fill in with informa-
tion about src. The
value of *flagsPtr
must be passed to
Tcl_ConvertElement.
char *dst (in) Place to copy con-
verted 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_ScanElement, pos-
sibly OR-ed with
TCL_DONT_USE_BRACES.
_________________________________________________________________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 interp->result
will point to an error message describing the problem (if |
interp was not NULL). If TCL_ERROR is returned then no
memory is allocated and *argvPtr is not modified.
Tcl 7.5 2
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)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_Con-
vertElement handles special characters by generating back-
slash 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
Tcl 7.5 3
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)
will produce an uglier result, it is useful in some spe-
cial situations, such as when Tcl_ConvertElement is being
used to generate a portion of an argument for a Tcl com-
mand. In this case, surrounding src with curly braces
would cause the command not to be parsed correctly.
KEYWORDS
backslash, convert, element, list, merge, split, strings
Tcl 7.5 4
