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.

       const 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.

SEE ALSO

       Tcl_ListObjGetElements(3tcl)

KEYWORDS

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

Tcl                                                    8.0                                   Tcl_SplitList(3tcl)