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 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
       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 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
       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.

       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