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Tcl_SplitList(3) Tcl Library Procedures Tcl_SplitList(3) ________________________________________________________________________________ NAME Tcl_SplitList, Tcl_Merge, Tcl_ScanElement, Tcl_ConvertElement, Tcl_Scan- CountedElement, 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 re- porting. 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 ele- ments 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 en- tries 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 to- gether into a single list. Each string will become a separate element of the list. const char *src (in) String that is to become an ele- ment 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 el- ement. 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 ex- tracting the arguments, Tcl_SplitList obeys the usual rules for backslash substitutions and braces. The area of memory pointed to by *argvPtr is dy- namically 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 success- fully parsed. If there was a syntax error in list, then TCL_ERROR is re- turned and the interpreter's result will point to an error message describ- ing 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 allo- cated 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 re- turned 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 re- sulting 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 de- termines how to use backslashes and braces when converting it to a list el- ement. 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 argu- ment must be the same as the value returned by Tcl_ScanElement. Tcl_Con- vertElement writes a proper list element to memory starting at *dst and re- turns 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 ele- ments. Tcl_ConvertElement uses one of two different approaches to handle the spe- cial 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 ele- ment 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(3) KEYWORDS backslash, convert, element, list, merge, split, strings Tcl 8.0 Tcl_SplitList(3)
NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | SEE ALSO | KEYWORDS
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