SetVar

Tcl_SetVar(3)               Tcl Library Procedures               Tcl_SetVar(3)



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

SYNOPSIS
       #include <tcl.h>

       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.

       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.
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DESCRIPTION
       These procedures may be used to create, modify, read, and delete Tcl
       variables from C code.  Tcl_SetVar and Tcl_SetVar2 will create a new
       variable or modify an existing one.  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), then NULL is returned.

       The name of the variable may be specified 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->result.  If this flag bit
              isn't set then no error message is left (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_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).  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_TraceVar


KEYWORDS
       array, interpreter, scalar, set, unset, variable



Tcl                                   7.4                        Tcl_SetVar(3)