Tcl_SplitList(3Tcl)Tcl_SplitList(3Tcl)NAME
Tcl_SplitList, Tcl_Merge, Tcl_ScanElement, Tcl_ConvertElement -
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.
char *src (in) String that is to become an element
of a list.
int *flagsPtr (in) Pointer to word to fill in with
information about src. The value of
*flagsPtr must be passed to
Tcl_ConvertElement.
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Tcl_SplitList(3Tcl)Tcl_SplitList(3Tcl)
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_ScanElement, possibly 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 constituent elements, returning
an array of pointers to the elements using argcPtr and argvPtr. While
extracting the arguments, Tcl_SplitList obeys the usual rules for
backslash substitutions and braces. The area of memory pointed to by
*argvPtr is dynamically allocated; in addition 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:
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_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 malloc(); the caller must eventually release
the space using free().
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Tcl_SplitList(3Tcl)Tcl_SplitList(3Tcl)
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 original string.
Tcl_ScanElement and Tcl_ConvertElement are the procedures that do all of
the real work of Tcl_Merge. Tcl_ScanElement scans its src argument and
determines how to use backslashes and braces when converting it to a list
element. It returns an overestimate of the number of characters required
to represent src as a list element, and it stores information in
*flagsPtr that is needed by Tcl_ConvertElement.
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_ConvertElement writes a proper list element to memory starting 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
contains unmatched braces. In these situations, Tcl_ConvertElement
handles special characters by generating 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.
KEYWORDS
backslash, convert, element, list, merge, split, strings
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