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Tcl Library Procedures Tcl_SplitList(3TCL)

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NAME

Tcl_SplitList, Tcl_Merge, Tcl_ScanElement,

Tcl_ConvertElement, Tcl_ScanCountedElement,

Tcl_ConvertCountedElement - manipulate Tcl lists

SYNOPSIS

#include

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 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 Tcl Last change: 8.0 1

Tcl Library Procedures Tcl_SplitList(3TCL)

elements of list. There will be *argcPtr valid entries in

the array, fol-

lowed by a NULL entry.

int argc (in) Number of ele-

ments 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 pre-

vious call to

Tcl_ScanElement,

possibly OR-ed

Tcl Last change: 8.0 2

Tcl Library Procedures Tcl_SplitList(3TCL)

with

TCL_DONT_USE_BRACES.

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DESCRIPTION

These procedures may be used to disassemble and reassemble

Tcl lists. Tcl_SplitList breaks a list up into its consti-

tuent elements, returning an array of pointers to the ele-

ments using argcPtr and argvPtr. While extracting the argu-

ments, 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 col-

lection 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 result-

ing string may not be the same as the original string passed Tcl Last change: 8.0 3

Tcl Library Procedures Tcl_SplitList(3TCL)

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 can't 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.

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

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes: Tcl Last change: 8.0 4

Tcl Library Procedures Tcl_SplitList(3TCL)

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| ATTRIBUTE TYPE | ATTRIBUTE VALUE|

|____________________|__________________|_

| Availability | runtime/tcl-8 |

|____________________|__________________|_

| Interface Stability| Uncommitted |

|____________________|_________________|

NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.0 5