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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 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 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.

       const char *const *argv (in)		  Array  of strings to merge together into a sin-
						  gle 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.
_________________________________________________________________

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 ele-
       ments  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:
	      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 differ-
       ently 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 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 output to be sure the first charac- |
       ter 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 beginning of a comment.  When a list |
       element is not the first element of a list, this quoting is not necessary.  When the call- |
       er can be sure that the element is not the first element of a list, it can disable quoting |
       of the leading hash character 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.

KEYWORDS
       backslash, convert, element, list, merge, split, strings

Tcl					       8.0				 Tcl_SplitList(3)
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