Tcl Library Procedures

NAME

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

SYNOPSIS

#include <tcl.h>

Tcl_Obj *
Tcl_ObjSetVar2(interp, part1Ptr, part2Ptr, newValuePtr, flags)

Tcl_Obj *
Tcl_ObjGetVar2(interp, part1Ptr, part2Ptr, flags)

char *
Tcl_SetVar(interp, varName, newValue, flags)

char *
Tcl_SetVar2(interp, name1, name2, newValue, flags)

char *
Tcl_GetVar(interp, varName, flags)

char *
Tcl_GetVar2(interp, name1, name2, flags)

int
Tcl_UnsetVar(interp, varName, flags)

int
Tcl_UnsetVar2(interp, name1, name2, flags)

ARGUMENTS

Tcl_Interp *interp (in)
Interpreter containing variable.

Tcl_Obj *part1Ptr (in)
Points to a Tcl object containing the variable's name. May refer to a scalar variable or an element of an array variable.

Tcl_Obj *part2Ptr (in)
If non-NULL, points to an object containing the name of an element within an array and part1Ptr must refer to an array variable.

char *varName (in)
Name of variable. 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.

char *varName (in)
Name of variable. 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.

char *newValue (in)
New value for variable.

int flags (in)
OR-ed combination of bits providing additional information for operation. See below for valid values.

char *name1 (in)
Name of scalar variable, or name of array variable if name2 is non-NULL.

char *name2 (in)
If non-NULL, gives name of element within array and name1 must refer to an array variable.

DESCRIPTION

These procedures may be used to create, modify, read, and delete Tcl variables from C code. Tcl_ObjSetVar2, Tcl_SetVar, and Tcl_SetVar2 will create a new variable or modify an existing one. Tcl_ObjSetVar2 sets the specified variable to the object referenced by newValuePtr and returns a pointer to the object which is the variable's new value. The reference count for the returned object is not incremented. If the caller needs to keep a reference to the object, say in a data structure, it must increment the reference count using Tcl_IncrRefCount. If an error occurs in setting the variable (e.g. an array variable is referenced without giving an index into the array), then NULL is returned.

The variable name specified to Tcl_ObjSetVar2 consists of two parts. part1Ptr contains the name of a scalar or array variable. If part2Ptr is NULL, the variable must be a scalar. If part2Ptr is not NULL, it contains the name of an element in the array named by part2Ptr. As a special case, if the flag TCL_PART1_NOT_PARSED is specified, part1Ptr 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_PART1_NOT_PARSED is given, part2Ptr should be NULL since the array and element names are taken from part2Ptr.

Tcl_SetVar and Tcl_SetVar2 resemble Tcl_ObjSetVar2 but take strings for the variable name and value, and return a string. Both of these procedures set the given variable to the value given by newValue, 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 newValue 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.

The name of the variable may be specified to Tcl_SetVar and Tcl_SetVar2 in either of two ways. If Tcl_SetVar is called, the variable name is given as a single string, varName. If varName 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 varName doesn't have parentheses as described above, then the entire string is treated as the name of a scalar variable. If Tcl_SetVar2 is called, then the array name and index have been separated by the caller into two separate strings, name1 and name2 respectively; if name2 is zero it means that a scalar variable is being referenced.

The flags argument may be used to specify any of several options to the procedures. It consists of an OR-ed combination of any of the following bits:

TCL_GLOBAL_ONLY
Under normal circumstances the procedures look up variables at the current level of procedure call for interp, or at global level if there is no call active. However, if this bit is set in flags then the variable is looked up at global level even if there is a procedure call active.

TCL_LEAVE_ERR_MSG
If an error is returned and this bit is set in flags, then an error message will be left in interp->objResult (if Tcl_ObjGetVar2 or Tcl_ObjSetVar2 are called) or in interp->result otherwise. The object error message in interp->objResult can be retrieved using Tcl_GetObjResult. If this flag bit isn't set then no error message is left (interp->objResult and interp->result will not be modified).

TCL_APPEND_VALUE
If this bit is set then newValue is appended to the current value, instead of replacing it. If the variable is currently undefined, then this bit is ignored.

TCL_LIST_ELEMENT
If this bit is set, then newValue 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 `` }'').

TCL_PART1_NOT_PARSED
This bit is meaningful only for Tcl_ObjGetVar2 and Tcl_ObjSetVar2. If this bit is set, then these procedures will parse part1Ptr to obtain both an array name and an element name. If the name in part1Ptr does not contain an open parenthesis and does not end with a close parenthesis, then the name is treated as the name of a scalar variable. Otherwise the parsed array and element names are used.

Tcl_ObjGetVar2 returns the value of the specified variable. Its arguments are treated the same way as those for Tcl_ObjSetVar2. It returns a pointer to the object which is the variable's value. The reference count for the returned object is not incremented. If the caller needs to keep a reference to the object, say in a data structure, it must increment the reference count using Tcl_IncrRefCount. If an error occurs in setting the variable (e.g. an array variable is referenced without giving an index into the array), then NULL is returned.

Tcl_GetVar and Tcl_GetVar2 resemble Tcl_ObjGetVar2 but take strings for the variable name and value, and return a string. They return the current value of a variable. The arguments to these procedures are treated in the same way as the arguments to Tcl_SetVar and Tcl_SetVar2. 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 Tcl_SetVar or Tcl_SetVar2). The only bits of flags that are used are TCL_GLOBAL_ONLY and TCL_LEAVE_ERR_MSG, both of which have the same meaning as for Tcl_SetVar. 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.

Tcl_UnsetVar and Tcl_UnsetVar2 may be used to remove a variable, so that future calls to Tcl_GetVar or Tcl_GetVar2 for the variable will return an error. The arguments to these procedures are treated in the same way as the arguments to Tcl_GetVar and Tcl_GetVar2. 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.

SEE ALSO

Tcl_GetObjResult, Tcl_TraceVar

KEYWORDS

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

Last change: 7.4

[ tcl8.0a1 | tk8.0a1 | X-ref ]

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