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_Convert-CountedElement Tcl_ConvertCountedElement
CountedElement - 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 elements 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 elements
ments of list. There will be *argcPtr valid entries in
the array, followed by a NULL entry.
int argc (in) Number of elements 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_ConvertEle-ment. Tcl_ConvertElement.
ment.
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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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 substitu-tions substitutions
tions 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 respon-sibility responsibility
sibility 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 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 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 convert-ing converting
ing it to a list element. It returns an overestimate of the number of characters required to repre-sent represent
sent src as a list element, and it stores information in *flagsPtr that is needed by Tcl_ConvertEle-ment. Tcl_ConvertElement.
ment.
Tcl_ConvertElement is a companion procedure to Tcl_ScanElement. It does the actual work of convert-ing converting
ing 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 pro-duces produces
duces 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 use-ful useful
ful 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_Con-vertElement, Tcl_ConvertElement,
vertElement, except the length of string src is specified by the length argument, and the string may
contain embedded nulls.
KEYWORDS
backslash, convert, element, list, merge, split, strings
Tcl 8.0 Tcl_SplitList(3)
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