Provided by: tcl8.5-doc_8.5.15-2ubuntu1_all bug

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