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.so man.macros

.TH Tcl_SplitList 3 7.5 Tcl "Tcl Library Procedures"

.BS

.SH NAME

Tcl_SplitList, Tcl_Merge, Tcl_ScanElement, Tcl_ConvertElement \- manipulate Tcl lists

.SH SYNOPSIS

.nf

\fB#include \fR

.sp

int

\fBTcl_SplitList\fR(\fIinterp, list, argcPtr, argvPtr\fR)

.sp

char *

\fBTcl_Merge\fR(\fIargc, argv\fR)

.sp

int

\fBTcl_ScanElement\fR(\fIsrc, flagsPtr\fR)

.VS

.sp

int

\fBTcl_ScanCountedElement\fR(\fIsrc, length, flagsPtr\fR)

.VE

.sp

int

\fBTcl_ConvertElement\fR(\fIsrc, dst, flags\fR)

.VS

.sp

int

\fBTcl_ConvertCountedElement\fR(\fIsrc, length, dst, flags\fR)

.VE

.SH ARGUMENTS

.AS Tcl_Interp ***argvPtr

.AP Tcl_Interp *interp out

.VS

Interpreter to use for error reporting.  If NULL, then no error message

is left.

.VE

.AP char *list in

Pointer to a string with proper list structure.

.AP int *argcPtr out

Filled in with number of elements in \fIlist\fR.

.AP char ***argvPtr out

\fI*argvPtr\fR will be filled in with the address of an array of

pointers to the strings that are the extracted elements of \fIlist\fR.

There will be \fI*argcPtr\fR valid entries in the array, followed by

a NULL entry.

.AP int argc in

Number of elements in \fIargv\fR.

.AP char **argv in

Array of strings to merge together into a single list.

Each string will become a separate element of the list.

.AP char *src in

String that is to become an element of a list.

.AP int *flagsPtr in

Pointer to word to fill in with information about \fIsrc\fR.

The value of *\fIflagsPtr\fR must be passed to \fBTcl_ConvertElement\fR.

.VS

.AP int length in

Number of bytes in string \fIsrc\fR.

.VE

.AP char *dst in

Place to copy converted list element.  Must contain enough characters

to hold converted string.

.AP int flags in

Information about \fIsrc\fR. Must be value returned by previous

call to \fBTcl_ScanElement\fR, possibly OR-ed

with \fBTCL_DONT_USE_BRACES\fR.

.BE

.SH DESCRIPTION

.PP

These procedures may be used to disassemble and reassemble Tcl lists.

\fBTcl_SplitList\fR breaks a list up into its constituent elements,

returning an array of pointers to the elements using

\fIargcPtr\fR and \fIargvPtr\fR.

While extracting the arguments, \fBTcl_SplitList\fR obeys the usual

rules for backslash substitutions and braces.  The area of

memory pointed to by \fI*argvPtr\fR 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 \fBTcl_SplitList\fR with

the following code:

.CS

int argc, code;

char *string;

char **argv;

\&...

code = Tcl_SplitList(interp, string, &argc, &argv);

.CE

Then you should eventually free the storage with a call like the

following:

.VS

.CS

Tcl_Free((char *) argv);

.CE

.VE

.PP

\fBTcl_SplitList\fR normally returns \fBTCL_OK\fR, which means the list was

successfully parsed.

If there was a syntax error in \fIlist\fR, then \fBTCL_ERROR\fR is returned

and \fIinterp->result\fR will point to an error message describing the

.VS

problem (if \fIinterp\fR was not NULL).

.VE

If \fBTCL_ERROR\fR is returned then no memory is allocated and \fI*argvPtr\fR

is not modified.

.PP

\fBTcl_Merge\fR is the inverse of \fBTcl_SplitList\fR:  it

takes a collection of strings given by \fIargc\fR

and \fIargv\fR and generates a result string

that has proper list structure.

This means that commands like \fBindex\fR may be used to

extract the original elements again.

In addition, if the result of \fBTcl_Merge\fR is passed to \fBTcl_Eval\fR,

it will be parsed into \fIargc\fR words whose values will

be the same as the \fIargv\fR strings passed to \fBTcl_Merge\fR.

\fBTcl_Merge\fR will modify the list elements with braces and/or

backslashes in order to produce proper Tcl list structure.

.VS

The result string is dynamically allocated

using \fBTcl_Alloc\fR;  the caller must eventually release the space

using \fBTcl_Free\fR.

.VE

.PP

If the result of \fBTcl_Merge\fR is passed to \fBTcl_SplitList\fR,

the elements returned by \fBTcl_SplitList\fR will be identical to

those passed into \fBTcl_Merge\fR.

However, the converse is not true:  if \fBTcl_SplitList\fR

is passed a given string, and the resulting \fIargc\fR and

\fIargv\fR are passed to \fBTcl_Merge\fR, the resulting string

may not be the same as the original string passed to \fBTcl_SplitList\fR.

This is because \fBTcl_Merge\fR may use backslashes and braces

differently than the original string.

.PP

\fBTcl_ScanElement\fR and \fBTcl_ConvertElement\fR are the

procedures that do all of the real work of \fBTcl_Merge\fR.

\fBTcl_ScanElement\fR scans its \fIsrc\fR 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 \fIsrc\fR as a list element, and

it stores information in \fI*flagsPtr\fR that is needed

by \fBTcl_ConvertElement\fR.

.PP

\fBTcl_ConvertElement\fR is a companion procedure to \fBTcl_ScanElement\fR.

It does the actual work of converting a string to a list element.

Its \fIflags\fR argument must be the same as the value returned

by \fBTcl_ScanElement\fR.

\fBTcl_ConvertElement\fR writes a proper list element to memory

starting at *\fIdst\fR and returns a count of the total number

of characters written, which will be no more than the result

returned by \fBTcl_ScanElement\fR.

\fBTcl_ConvertElement\fR 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.

.PP

\fBTcl_ConvertElement\fR uses one of two different approaches to

handle the special characters in \fIsrc\fR.  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 \fIsrc\fR contains unmatched braces.

In these situations, \fBTcl_ConvertElement\fR 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 \fBTcl_ScanElement\fR with

\fBTCL_DONT_USE_BRACES\fR.

Although this will produce an uglier result, it is useful in some

special situations, such as when \fBTcl_ConvertElement\fR is being

used to generate a portion of an argument for a Tcl command.

In this case, surrounding \fIsrc\fR with curly braces would cause

the command not to be parsed correctly.

.PP

.VS

\fBTcl_ScanCountedElement\fR and \fBTcl_ConvertCountedElement\fR are

the same as \fBTcl_ScanElement\fR and \fBTcl_ConvertElement\fR, except

the length of string \fIsrc\fR is specified by the \fIlength\fR

argument, and the string may contain embedded nulls.

.VE

.SH KEYWORDS

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