Tcl_SplitList(3)
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)
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NAME
Tcl_SplitList, Tcl_Merge, Tcl_ScanElement,
Tcl_ConvertElement, Tcl_ScanCountedElement,
Tcl_ConvertCountedElement - 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_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
Tcl Last change: 8.0 1
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)
elements of list.
There will be
*argcPtr valid
entries in the
array, followed
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 separate
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
information about
src. The value
of *flagsPtr must
be passed to
Tcl_ConvertElement.
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_ScanElement,
possibly OR-ed
with
TCL_DONT_USE_BRACES.
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Tcl Last change: 8.0 2
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)
DESCRIPTION
These procedures may be used to disassemble and reassemble
Tcl lists. Tcl_SplitList breaks a list up into its consti-
tuent elements, returning an array of pointers to the ele-
ments using argcPtr and argvPtr. While extracting the argu-
ments, 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:
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 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 col-
lection 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 result-
ing 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
Tcl Last change: 8.0 3
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)
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 cannot 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.
By default, Tcl_ConvertElement will use quoting in its out- |
put to be sure the first character of an element is not the |
hash character ("#".) This is to be sure the first element |
of any list passed to eval is not mis-parsed as the begin- |
ning of a comment. When a list element is not the first |
element of a list, this quoting is not necessary. When the |
caller can be sure that the element is not the first element |
of a list, it can disable quoting of the leading hash char- |
acter by OR-ing the flag value returned by Tcl_ScanElement |
with TCL_DONT_QUOTE_HASH.
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 argument,
and the string may contain embedded nulls.
Tcl Last change: 8.0 4
Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3)
KEYWORDS
backslash, convert, element, list, merge, split, strings
Tcl Last change: 8.0 5
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