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 single list.  Each string will become a separate ele-
						  ment 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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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:
	      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 argu-
       ment 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 start-
       ing  at	*dst and returns a count of the total number of characters written, which will be no more than the result returned by Tcl_ScanEle-
       ment.  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 gen-
       erate 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 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 beginning 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 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)