DOKK / manpages / debian 10 / tcl8.6-doc / Tcl_UnsetVar.3tcl.en
Tcl_SetVar(3tcl) Tcl Library Procedures Tcl_SetVar(3tcl) 







Tcl_SetVar2Ex, Tcl_SetVar, Tcl_SetVar2, Tcl_ObjSetVar2,
    Tcl_GetVar2Ex, Tcl_GetVar, Tcl_GetVar2, Tcl_ObjGetVar2, Tcl_UnsetVar,
    Tcl_UnsetVar2 - manipulate Tcl variables








#include <tcl.h>

Tcl_Obj *
Tcl_SetVar2Ex(interp, name1, name2, newValuePtr, flags)

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

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

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

Tcl_Obj *
Tcl_GetVar2Ex(interp, name1, name2, flags)

const char *
Tcl_GetVar(interp, varName, flags)

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

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

int
Tcl_UnsetVar(interp, varName, flags)

int
Tcl_UnsetVar2(interp, name1, name2, flags)









  
Tcl_Interp *interp (in)

  
Interpreter containing variable.

  
const char *name1 (in)

  
Contains the name of an array variable (if name2 is non-NULL) or
      (if name2 is NULL) either the name of a scalar variable or a
      complete name including both variable name and index. May include
      :: namespace qualifiers to specify a variable in a particular
      namespace.

  
const char *name2 (in)

  
If non-NULL, gives name of element within array; in this case name1
      must refer to an array variable.

  
Tcl_Obj *newValuePtr (in)

  
Points to a Tcl value containing the new value for the variable.

  
int flags (in)

  
OR-ed combination of bits providing additional information. See below for
      valid values.

  
const char *varName (in)

  
Name of variable. May include :: namespace qualifiers to specify a
      variable in a particular namespace. May refer to a scalar variable or an
      element of an array.

  
const char *newValue (in)

  
New value for variable, specified as a null-terminated string. A copy of
      this value is stored in the variable.

  
Tcl_Obj *part1Ptr (in)

  
Points to a Tcl value containing the variable's name. The name may include
      a series of :: namespace qualifiers to specify a variable in a
      particular namespace. May refer to a scalar variable or an element of an
      array variable.

  
Tcl_Obj *part2Ptr (in)

  
If non-NULL, points to a value containing the name of an element within an
      array and part1Ptr must refer to an array variable.
    
    

    

  










These procedures are used to create, modify, read, and delete Tcl
    variables from C code.


Tcl_SetVar2Ex, Tcl_SetVar, Tcl_SetVar2, and
    Tcl_ObjSetVar2 will create a new variable or modify an existing one.
    These procedures set the given variable to the value given by
    newValuePtr or newValue and return a pointer to the variable's
    new value, which is stored in Tcl's variable structure. Tcl_SetVar2Ex
    and Tcl_ObjSetVar2 take the new value as a Tcl_Obj and return a
    pointer to a Tcl_Obj. Tcl_SetVar and Tcl_SetVar2 take the new
    value as a string and return a string; they are usually less efficient than
    Tcl_ObjSetVar2. Note that the return value may be different than the
    newValuePtr or newValue argument, due to modifications made by
    write traces. If an error occurs in setting the variable (e.g. an array
    variable is referenced without giving an index into the array) NULL is
    returned and an error message is left in interp's result if the
    TCL_LEAVE_ERR_MSG flag bit is set.


Tcl_GetVar2Ex, Tcl_GetVar, Tcl_GetVar2, and
    Tcl_ObjGetVar2 return the current value of a variable. The arguments
    to these procedures are treated in the same way as the arguments to the
    procedures described above. Under normal circumstances, the return value is
    a pointer to the variable's value. For Tcl_GetVar2Ex and
    Tcl_ObjGetVar2 the value is returned as a pointer to a Tcl_Obj. For
    Tcl_GetVar and Tcl_GetVar2 the value is returned as a string;
    this is usually less efficient, so Tcl_GetVar2Ex or
    Tcl_ObjGetVar2 are preferred. If an error occurs while reading the
    variable (e.g. the variable does not exist or an array element is specified
    for a scalar variable), then NULL is returned and an error message is left
    in interp's result if the TCL_LEAVE_ERR_MSG flag bit is
    set.


Tcl_UnsetVar and Tcl_UnsetVar2 may be used to remove
    a variable, so that future attempts to read the variable will return an
    error. The arguments to these procedures are treated in the same way as the
    arguments to the procedures above. If the variable is successfully removed
    then TCL_OK is returned. If the variable cannot be removed because it
    does not exist then TCL_ERROR is returned and an error message is
    left in interp's result if the TCL_LEAVE_ERR_MSG flag
    bit is set. 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.


The name of a variable may be specified to these procedures in
    four ways:



  
[1]

  
If Tcl_SetVar, Tcl_GetVar, or Tcl_UnsetVar is
      invoked, 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 does not have parentheses as described above, then the
      entire string is treated as the name of a scalar variable.

  
[2]

  
If the name1 and name2 arguments are provided and
      name2 is non-NULL, then an array element is specified and the array
      name and index have already been separated by the caller: name1
      contains the name and name2 contains the index. An error is
      generated if name1 contains an open parenthesis and ends with a
      close parenthesis (array element) and name2 is non-NULL.

  
[3]

  
If name2 is NULL, name1 is treated just like varName
      in case [1] above (it can be either a scalar or an array element variable
      name).




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



  

  
Under normal circumstances the procedures look up variables as follows. If
      a procedure call is active in interp, the variable is looked up at
      the current level of procedure call. Otherwise, the variable is looked up
      first in the current namespace, then in the global namespace. However, if
      this bit is set in flags then the variable is looked up only in the
      global namespace even if there is a procedure call active. If both
      TCL_GLOBAL_ONLY and TCL_NAMESPACE_ONLY are given,
      TCL_GLOBAL_ONLY is ignored.

  

  
If this bit is set in flags then the variable is looked up only in
      the current namespace; if a procedure is active its variables are ignored,
      and the global namespace is also ignored unless it is the current
      namespace.

  

  
If an error is returned and this bit is set in flags, then an error
      message will be left in the interpreter's result, where it can be
      retrieved with Tcl_GetObjResult or Tcl_GetStringResult. If
      this flag bit is not set then no error message is left and the
      interpreter's result will not be modified.

  

  
If this bit is set then newValuePtr or newValue is appended
      to the current value instead of replacing it. If the variable is currently
      undefined, then the bit is ignored. This bit is only used by the
      Tcl_Set* procedures.

  

  
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 “ }”). When appending, the original value of the
      variable must also be a valid list, so that the operation is the appending
      of a new list element onto a list.




Tcl_GetVar and Tcl_GetVar2 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). Tcl_GetVar and
    Tcl_GetVar2 use the flag bits 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 does not 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 does
    not 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.










Tcl_GetObjResult, Tcl_GetStringResult, Tcl_TraceVar










array, get variable, interpreter, scalar, set, unset, value,
    variable







  

    8.1
    Tcl