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 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  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