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Tcl_SplitList(3)		      Tcl Library Procedures			 Tcl_SplitList(3)

_________________________________________________________________________________________________

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 struc-
						   ture.

       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 can't be used in some situations, such as
       when src contains unmatched braces.  In these situations, Tcl_ConvertElement handles  spe-
       cial  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.

       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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