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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_Convert-CountedElement Tcl_ConvertCountedElement
       CountedElement - 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_ConvertEle-ment. Tcl_ConvertElement.
                                                  ment.

       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 substitu-tions substitutions
       tions  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  respon-sibility responsibility
       sibility  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 convert-ing converting
       ing  it to a list element.  It returns an overestimate of the number of characters required to repre-sent represent
       sent src as a list element, and it stores information in *flagsPtr that is needed by  Tcl_ConvertEle-ment. Tcl_ConvertElement.
       ment.

       Tcl_ConvertElement  is a companion procedure to Tcl_ScanElement.  It does the actual work of convert-ing converting
       ing 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  pro-duces produces
       duces  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_Con-vertElement, Tcl_ConvertElement,
       vertElement,  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)