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.so man.macros

.TH Tcl_SetVar 3 7.4 Tcl "Tcl Library Procedures"

.BS

.SH NAME

Tcl_SetVar, Tcl_SetVar2, Tcl_GetVar, Tcl_GetVar2, Tcl_UnsetVar, Tcl_UnsetVar2 \- manipulate Tcl variables

.SH SYNOPSIS

.nf

\fB#include \fR

.sp

char *

\fBTcl_SetVar\fR(\fIinterp, varName, newValue, flags\fR)

.sp

char *

\fBTcl_SetVar2\fR(\fIinterp, name1, name2, newValue, flags\fR)

.sp

char *

\fBTcl_GetVar\fR(\fIinterp, varName, flags\fR)

.sp

char *

\fBTcl_GetVar2\fR(\fIinterp, name1, name2, flags\fR)

.sp

int

\fBTcl_UnsetVar\fR(\fIinterp, varName, flags\fR)

.sp

int

\fBTcl_UnsetVar2\fR(\fIinterp, name1, name2, flags\fR)

.SH ARGUMENTS

.AS Tcl_Interp *newValue

.AP Tcl_Interp *interp in

Interpreter containing variable.

.AP char *varName in

Name of variable.

May include a series of \fB::\fR namespace qualifiers

to specify a variable in a particular namespace.

May refer to a scalar variable or an element of

an array variable.

If the name references an element of an array, then it

must be in writable memory:  Tcl will make temporary modifications

to it while looking up the name.

.AP char *newValue in

New value for variable.

.AP int flags in

OR-ed combination of bits providing additional information for

operation. See below for valid values.

.AP char *name1 in

Name of scalar variable, or name of array variable if \fIname2\fR

is non-NULL.

May include a series of \fB::\fR namespace qualifiers

to specify a variable in a particular namespace.

.AP char *name2 in

If non-NULL, gives name of element within array and \fIname1\fR

must refer to an array variable.

.BE

.SH DESCRIPTION

.PP

These procedures may be used to create, modify, read, and delete

Tcl variables from C code.

.PP

Note that \fBTcl_GetVar\fR and \fBTcl_SetVar\fR

have been largely replaced by the

object-based procedures \fBTcl_ObjGetVar2\fR and \fBTcl_ObjSetVar2\fR.

Those object-based procedures read, modify, and create

a variable whose name is held in a Tcl object instead of a string.

They also return a pointer to the object

which is the variable's value instead of returning a string.

Operations on objects can be faster since objects

hold an internal representation that can be manipulated more efficiently.

.PP

\fBTcl_SetVar\fR and \fBTcl_SetVar2\fR

will create a new variable or modify an existing one.

Both of these procedures set the given variable to the value

given by \fInewValue\fR, and they return a pointer to a

copy of the variable's new value, which is stored in Tcl's

variable structure.

Tcl keeps a private copy of the variable's value, so the caller

may change \fInewValue\fR after these procedures return without

affecting the value of the variable.

If an error occurs in setting the variable (e.g. an array

variable is referenced without giving an index into the array),

they return NULL.

.PP

The name of the variable may be specified to

\fBTcl_SetVar\fR and \fBTcl_SetVar2\fR in either of two ways.

If \fBTcl_SetVar\fR is called, the variable name is given as

a single string, \fIvarName\fR.

If \fIvarName\fR contains an open parenthesis and ends with a

close parenthesis, then the value between the parentheses is

treated as an index (which can have any string value) and

the characters before the first open

parenthesis are treated as the name of an array variable.

If \fIvarName\fR doesn't have parentheses as described above, then

the entire string is treated as the name of a scalar variable.

If \fBTcl_SetVar2\fR is called, then the array name and index

have been separated by the caller into two separate strings,

\fIname1\fR and \fIname2\fR respectively;  if \fIname2\fR is

zero it means that a scalar variable is being referenced.

.PP

The \fIflags\fR argument may be used to specify any of several

options to the procedures.

It consists of an OR-ed combination of the following bits.

Note that the flag bit TCL_PARSE_PART1 is only meaningful

for the procedures Tcl_SetVar2 and Tcl_GetVar2.

.TP

\fBTCL_GLOBAL_ONLY\fR

Under normal circumstances the procedures look up variables as follows:

If a procedure call is active in \fIinterp\fR,

a variable is looked up at the current level of procedure call.

Otherwise, a variable is looked up first in the current namespace,

then in the global namespace.

However, if this bit is set in \fIflags\fR then the variable

is looked up only in the global namespace

even if there is a procedure call active.

If both \fBTCL_GLOBAL_ONLY\fR and \fBTCL_NAMESPACE_ONLY\fR are given,

\fBTCL_GLOBAL_ONLY\fR is ignored.

.TP

\fBTCL_NAMESPACE_ONLY\fR

Under normal circumstances the procedures look up variables as follows:

If a procedure call is active in \fIinterp\fR,

a variable is looked up at the current level of procedure call.

Otherwise, a variable is looked up first in the current namespace,

then in the global namespace.

However, if this bit is set in \fIflags\fR then the variable

is looked up only in the current namespace

even if there is a procedure call active.

.TP

\fBTCL_LEAVE_ERR_MSG\fR

If an error is returned and this bit is set in \fIflags\fR, then

an error message will be left in the interpreter's result,

where it can be retrieved with \fBTcl_GetObjResult\fR

or \fBTcl_GetStringResult\fR.

If this flag bit isn't set then no error message is left

and the interpreter's result will not be modified.

.TP

\fBTCL_APPEND_VALUE\fR

If this bit is set then \fInewValue\fR is appended to the current

value, instead of replacing it.

If the variable is currently undefined, then this bit is ignored.

.TP

\fBTCL_LIST_ELEMENT\fR

If this bit is set, then \fInewValue\fR is converted to a valid

Tcl list element before setting (or appending to) the variable.

A separator space is appended before the new list element unless

the list element is going to be the first element in a list or

sublist (i.e. the variable's current value is empty, or contains

the single character ``{'', or ends in `` }'').

.TP

\fBTCL_PARSE_PART1\fR

If this bit is set when calling \fITcl_SetVar2\fR and \fITcl_GetVar2\fR,

\fIname1\fR may contain both an array and an element name:

if the name contains an open parenthesis and ends with a

close parenthesis, then the value between the parentheses is

treated as an element name (which can have any string value) and

the characters before the first open

parenthesis are treated as the name of an array variable.

If the flag TCL_PARSE_PART1 is given,

\fIname2\fR should be NULL since the array and element names

are taken from \fIname1\fR.

.PP

\fBTcl_GetVar\fR and \fBTcl_GetVar2\fR

return the current value of a variable.

The arguments to these procedures are treated in the same way

as the arguments to \fBTcl_SetVar\fR and \fBTcl_SetVar2\fR.

Under normal circumstances, the return value is a pointer

to the variable's value (which is stored in Tcl's variable

structure and will not change before the next call to \fBTcl_SetVar\fR

or \fBTcl_SetVar2\fR).

\fBTcl_GetVar\fR and \fBTcl_GetVar2\fR use the flag bits TCL_GLOBAL_ONLY

and TCL_LEAVE_ERR_MSG, both of

which have

the same meaning as for \fBTcl_SetVar\fR.

In addition, \fBTcl_GetVar2\fR uses the bit TCL_PARSE_PART1,

which has the same meaning as for \fBTcl_SetVar2\fR.

If an error occurs in reading the variable (e.g. the variable

doesn't exist or an array element is specified for a scalar

variable), then NULL is returned.

.PP

\fBTcl_UnsetVar\fR and \fBTcl_UnsetVar2\fR may be used to remove

a variable, so that future calls to \fBTcl_GetVar\fR or \fBTcl_GetVar2\fR

for the variable will return an error.

The arguments to these procedures are treated in the same way

as the arguments to \fBTcl_GetVar\fR and \fBTcl_GetVar2\fR.

If the variable is successfully removed then TCL_OK is returned.

If the variable cannot be removed because it doesn't exist then

TCL_ERROR is returned.

If an array element is specified, the given element is removed

but the array remains.

If an array name is specified without an index, then the entire

array is removed.

.SH "SEE ALSO"

Tcl_GetObjResult, Tcl_GetStringResult, Tcl_ObjGetVar2, Tcl_ObjSetVar2, Tcl_TraceVar

.SH KEYWORDS

array, interpreter, object, scalar, set, unset, variable