HPUX LinkVar[3]
Tcl_LinkVar(3) Tcl Tcl_LinkVar(3)
Tcl Library Procedures Tcl Library Procedures
7.0
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NAME
Tcl_LinkVar, Tcl_UnlinkVar - link Tcl variable to C variable
SYNOPSIS
#include <tcl.h>
int
Tcl_LinkVar(interp, varName, addr, type)
Tcl_UnlinkVar(interp, varName)
ARGUMENTS
Tcl_Interp *interp (in) Interpreter that contains varName.
Also used by Tcl_LinkVar to return
error messages.
char *varName (in) Name of global variable.
char *addr (in) Address of C variable that is to be
linked to varName.
int type (in) Type of C variable. Must be one of
TCL_LINK_INT, TCL_LINK_DOUBLE,
TCL_LINK_BOOLEAN, or
TCL_LINK_STRING, optionally OR'ed
with TCL_LINK_READ_ONLY to make Tcl
variable read-only.
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DESCRIPTION
Tcl_LinkVar uses variable traces to keep the Tcl variable named by
varName in sync with the C variable at the address given by addr.
Whenever the Tcl variable is read the value of the C variable will be
returned, and whenever the Tcl variable is written the C variable will
be updated to have the same value. Tcl_LinkVar normally returns
TCL_OK; if an error occurs while setting up the link (e.g. because
varName is the name of array) then TCL_ERROR is returned and interp-
>result contains an error message.
The type argument specifies the type of the C variable, and must have
one of the following values, optionally OR'ed with TCL_LINK_READ_ONLY:
TCL_LINK_INT
The C variable is of type int. Any value written into the Tcl
variable must have a proper integer form acceptable to
Tcl_GetInt; attempts to write non-integer values into varName
- 1 - Formatted: August 11, 1996
Tcl_LinkVar(3) Tcl Tcl_LinkVar(3)
Tcl Library Procedures Tcl Library Procedures
7.0
will be rejected with Tcl errors.
TCL_LINK_DOUBLE
The C variable is of type double. Any value written into the Tcl
variable must have a proper real form acceptable to
Tcl_GetDouble; attempts to write non-real values into varName
will be rejected with Tcl errors.
TCL_LINK_BOOLEAN
The C variable is of type int. If its value is zero then it will
read from Tcl as ``0''; otherwise it will read from Tcl as ``1''.
Whenver varName is modified, the C variable will be set to a 0 or
1 value. Any value written into the Tcl variable must have a
proper boolean form acceptable to Tcl_GetBoolean; attempts to
write non-boolean values into varName will be rejected with Tcl
errors.
TCL_LINK_STRING
The C variable is of type char *. If its value is not null then
it must be a pointer to a string allocated with malloc. Whenever
the Tcl variable is modified the current C string will be freed
and new memory will be allocated to hold a copy of the variable's
new value. If the C variable contains a null pointer then the
Tcl variable will read as ``NULL''.
If the TCL_LINK_READ_ONLY flag is present in type then the variable
will be read-only from Tcl, so that its value can only be changed by
modifying the C variable. Attempts to write the variable from Tcl
will be rejected with errors.
KEYWORDS
boolean, integer, link, read-only, real, string, variable
- 2 - Formatted: August 11, 1996