'\"
'\" Copyright (c) 1995-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" SCCS: @(#) GetFile.3 1.8 96/03/25 20:03:31
'\" 
.so man.macros
.TH Tcl_GetFile 3 7.5 Tcl "Tcl Library Procedures"
.BS
.SH NAME
Tcl_GetFile, Tcl_FreeFile, Tcl_GetFileInfo \- procedures to manipulate generic file handles
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
Tcl_File
\fBTcl_GetFile\fR(\fIosHandle, type\fR)
.sp
\fBTcl_FreeFile\fR(\fIhandle\fR)
.sp
ClientData
\fBTcl_GetFileInfo\fR(\fIhandle, typePtr\fR)
.sp
ClientData
\fBTcl_GetNotifierData\fR(\fIhandle, freeProcPtr\fR)
.sp
\fBTcl_SetNotifierData\fR(\fIhandle, freeProc, clientData\fR)
.SH ARGUMENTS
.AS Tcl_FileFreeProc **freeProcPtr
.AP ClientData osHandle  in
Platform-specific file handle to be associated with the generic file handle.
.AP int type in
The type of platform-specific file handle associated with the generic file
handle.  See below for a list of valid types.
.AP Tcl_File handle in
Generic file handle associated with platform-specific file information.
.AP int *typePtr in/out
If \fI*typePtr\fR is not NULL, then the specified word is set to
contain the type associated with \fIhandle\fR.
.AP Tcl_FileFreeProc *freeProc in
Procedure to call when \fIhandle\fR is deleted.
.AP Tcl_FileFreeProc **freeProcPtr in/out
Pointer to location in which to store address of current free procedure
for file handle.  Ignored if NULL.
.AP ClientData clientData in
Arbitrary one-word value associated with the given file handle. This
data is owned by the caller.
.BE

.SH DESCRIPTION
.PP
A \fBTcl_File\fR is an opaque handle used to refer to files in a
platform independent way in Tcl routines like
\fBTcl_CreateFileHandler\fR.  A file handle has an associated
platform-dependent \fIosHandle\fR, a \fItype\fR and additional private
data used by the notifier to generate events for the file.  The type
is an integer that determines how the platform-specific drivers will
interpret the \fIosHandle\fR.  The types that are defined by the core
are:
.TP 22
\fBTCL_UNIX_FD\fR
The \fIosHandle\fR is a Unix file descriptor.
.TP 22
\fBTCL_MAC_FILE\fR
The file is a Macintosh file handle.
.TP 22
\fBTCL_WIN_FILE\fR
The \fIosHandle\fR is a Windows normal file \fBHANDLE\fR.
.TP 22
\fBTCL_WIN_PIPE\fR
The \fIosHandle\fR is a Windows anonymous pipe \fBHANDLE\fR.
.TP 22
\fBTCL_WIN_SOCKET\fR
The \fIosHandle\fR is a Windows \fBSOCKET\fR.
.TP 22
\fBTCL_WIN_CONSOLE\fR
The \fIosHandle\fR is a Windows console buffer \fBHANDLE\fR.
.PP
\fBTcl_GetFile\fR locates the file handle corresponding to a particular
\fIosHandle\fR and a \fItype\fR.  If a file handle already existed for the
given file, then that handle will be returned.  If this is the first time that
the file handle for a particular file is being retrieved, then a new file
handle will be allocated and returned.
.PP
When a file handle is no longer in use, it should be deallocated with
a call to \fBTcl_FreeFile\fR.  A call to this function will invoke the
notifier free procedure \fIproc\fR, if there is one.  After the
notifier has cleaned up, any resources used by the file handle will be
deallocated.  \fBTcl_FreeFile\fR will not close the platform-specific
\fIosHandle\fR.
.PP
\fBTcl_GetFileInfo\fR may be used to retrieve the platform-specific
\fIosHandle\fR and type associated with a file handle.  If
\fItypePtr\fR is not NULL, then the word at \fI*typePtr\fR is set to
the type of the file handle.  The return value of the function is the
associated platform-specific \fIosHandle\fR.  Note that this function
may be used to extract the platform-specific file handle from a
\fBTcl_File\fR so that it may be used in external interfaces.
However, programs written using this interface will be
platform-specific.
.PP
The \fBTcl_SetNotifierData\fR and \fBTcl_GetNotifierData\fR procedures are
intended to be used only by notifier writers.  See the
\fITcl_CreateEventSource(3)\fR manual entry for more information on
the notifier.
.PP
\fBTcl_SetNotifierData\fR may be used by notifier writers to associate
notifier-specific information with a \fBTcl_File\fR.  The \fIdata\fR
argument specifies a word that may be retrieved with a later call to
\fBTcl_GetNotifierData\fR.  If the \fIfreeProc\fR argument is non-NULL
it specifies the address of a procedure to invoke when the
\fBTcl_File\fR is deleted.  \fIfreeProc\fR should have arguments and
result that match the type \fBTcl_FileFreeProc\fR:
.CS
typedef void Tcl_FileFreeProc(
	ClientData \fIclientData\fR);
.CE
When \fIfreeProc\fR is invoked the \fIclientData\fR argument will be
the same as the corresponding argument passed to
\fBTcl_SetNotifierData\fR.
.PP
\fBTcl_GetNotifierData\fR returns the \fIclientData\fR associated with
the given \fBTcl_File\fR, and if the \fIfreeProcPtr\fR field is
non-\fBNULL\fR, the address indicated by it gets the address of the
free procedure stored with this file.

.SH KEYWORDS
generic file handle, file type, file descriptor, notifier