442 lines
19 KiB
Groff
442 lines
19 KiB
Groff
'\"
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'\" Copyright (c) 1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) OpenFileChnl.3 1.27 96/03/22 14:55:07
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.so man.macros
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.TH Tcl_OpenFileChannel 3 7.5 Tcl "Tcl Library Procedures"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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Tcl_OpenFileChannel, Tcl_OpenCommandChannel, Tcl_Close, Tcl_Read, Tcl_Gets, Tcl_Write, Tcl_Flush, Tcl_Seek, Tcl_Tell, Tcl_Eof, Tcl_InputBlocked, Tcl_GetChannelOption, Tcl_SetChannelOption \- buffered I/O facilities using channels
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.SH SYNOPSIS
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.nf
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\fB#include <tcl.h>\fR
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.sp
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typedef ... Tcl_Channel;
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.sp
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Tcl_Channel
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\fBTcl_OpenFileChannel\fR(\fIinterp, fileName, mode, permissions\fR)
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.sp
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Tcl_Channel
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\fBTcl_OpenCommandChannel\fR(\fIinterp, argc, argv, flags\fR)
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.sp
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Tcl_Channel
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\fBTcl_MakeFileChannel\fR(\fIinOsFile, outOsFile, readOrWrite\fR)
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.sp
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Tcl_Channel
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\fBTcl_GetChannel\fR(\fIinterp, channelName, modePtr\fR)
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.sp
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void
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\fBTcl_RegisterChannel\fR(\fIinterp, channel\fR)
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.sp
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int
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\fBTcl_UnregisterChannel\fR(\fIinterp, channel\fR)
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.sp
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int
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\fBTcl_Close\fR(\fIinterp, channel\fR)
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.sp
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int
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\fBTcl_Read\fR(\fIchannel, buf, toRead\fR)
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.sp
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int
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\fBTcl_Gets\fR(\fIchannel, lineRead\fR)
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.sp
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int
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\fBTcl_Write\fR(\fIchannel, buf, toWrite\fR)
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.sp
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int
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\fBTcl_Flush\fR(\fIchannel\fR)
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.sp
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int
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\fBTcl_Seek\fR(\fIchannel, offset, seekMode\fR)
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.sp
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int
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\fBTcl_Tell\fR(\fIchannel\fR)
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.sp
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int
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\fBTcl_GetChannelOption\fR(\fIchannel, optionName, optionValue\fR)
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.sp
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int
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\fBTcl_SetChannelOption\fR(\fIinterp, channel, optionName, newValue\fR)
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.sp
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int
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\fBTcl_Eof\fR(\fIchannel\fR)
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.sp
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int
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\fBTcl_InputBlocked\fR(\fIchannel\fR)
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.sp
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int
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\fBTcl_InputBuffered\fR(\fIchannel\fR)
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.sp
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.SH ARGUMENTS
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.AS Tcl_ChannelType newClientProcPtr in
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.AP Tcl_Interp *interp in
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Used for error reporting and to look up a channel registered in it.
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.AP char *fileName in
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The name of a local or network file.
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.AP char *mode in
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Specifies how the file is to be accessed. May have any of the
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values allowed for the \fImode\fR argument to the Tcl
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\fBopen\fR command.
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For \fBTcl_OpenCommandChannel\fR, may be NULL.
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.AP int permissions in
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POSIX-style permission flags such as 0644.
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If a new file is created, these permissions will be set on the
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created file.
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.AP int argc in
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The number of elements in \fIargv\fR.
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.AP char **argv in
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Arguments for constructing a command pipeline.
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These values have the same meaning as the non-switch arguments
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to the Tcl \fBexec\fR command.
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.AP int flags in
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Specifies the disposition of the stdio handles in pipeline: OR-ed
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combination of \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, \fBTCL_STDERR\fR,
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and \fBTCL_ENFORCE_MODE\fR. If \fBTCL_STDIN\fR is set, stdin for
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the first child in the pipe is the pipe channel, otherwise it is the same
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as the standard input of the invoking process; likewise for
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\fBTCL_STDOUT\fR and \fBTCL_STDERR\fR. If \fBTCL_ENFORCE_MODE\fR is not set,
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then the pipe can redirect stdio handles to override the stdio handles for
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which \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR and \fBTCL_STDERR\fR have been set.
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If it is set, then such redirections cause an error.
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.AP ClientData inOsFile in
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Operating system specific handle for input from a file. For Unix this is a
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file descriptor, for Windows it is a HANDLE, etc.
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.AP ClientData outOsFile in
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Operating system specific handle for output to a file.
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.AP int readOrWrite in
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OR-ed combination of \fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR to indicate
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which of \fIinOsFile\fR and \fIoutOsFile\fR contains a valid value.
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.AP int *modePtr out
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Points at an integer variable that will receive an OR-ed combination of
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\fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR denoting whether the channel is
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open for reading and writing.
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.AP Tcl_Channel channel in
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A Tcl channel for input or output. Must have been the return value
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from a procedure such as \fBTcl_OpenFileChannel\fR.
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.AP char *buf in
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An array of bytes in which to store channel input, or from which
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to read channel output.
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.AP int toRead in
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The number of bytes to read from the channel.
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.AP Tcl_DString *lineRead in
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A pointer to a Tcl dynamic string in which to store the line read from the
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channel. Must have been initialized by the caller.
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.AP int toWrite in
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The number of bytes to read from \fIbuf\fR and output to the channel.
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.AP int offset in
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How far to move the access point in the channel at which the next input or
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output operation will be applied, measured in bytes from the position
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given by \fIseekMode\fR. May be either positive or negative.
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.AP int seekMode in
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Relative to which point to seek; used with \fIoffset\fR to calculate the new
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access point for the channel. Legal values are \fBSEEK_SET\fR,
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\fBSEEK_CUR\fR, and \fBSEEK_END\fR.
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.AP char *optionName in
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The name of an option applicable to this channel, such as \fB\-blocking\fR.
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May have any of the values accepted by the \fBfconfigure\fR command.
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.AP Tcl_DString *optionValue in
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Where to store the value of an option or a list of all options and their
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values. Must have been initialized by the caller.
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.AP char *newValue in
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New value for the option given by \fIoptionName\fR.
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.BE
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.SH DESCRIPTION
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.PP
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The Tcl channel mechanism provides a device-independent and
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platform-independent mechanism for performing buffered input
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and output operations on a variety of file, socket, and device
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types.
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The channel mechanism is extensible to new channel types, by
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providing a low level channel driver for the new type; the channel driver
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interface is described in the manual entry for \fBTcl_CreateChannel\fR. The
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channel mechanism provides a buffering scheme modelled after
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Unix's standard I/O, and it also allows for nonblocking I/O on
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channels.
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.PP
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The procedures described in this manual entry comprise the C APIs of the
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generic layer of the channel architecture. For a description of the channel
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driver architecture and how to implement channel drivers for new types of
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channels, see the manual entry for \fBTcl_CreateChannel\fR.
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.SH TCL_OPENFILECHANNEL
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.PP
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\fBTcl_OpenFileChannel\fR opens a file specified by \fIfileName\fR and
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returns a channel handle that can be used to perform input and output on
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the file. This API is modelled after the \fBfopen\fR procedure of
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the Unix standard I/O library.
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The syntax and meaning of all arguments is similar to those
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given in the Tcl \fBopen\fR command when opening a file.
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If an error occurs while opening the channel, \fBTcl_OpenFileChannel\fR
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returns NULL and records a POSIX error code that can be
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retrieved with \fBTcl_GetErrno\fR.
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In addition, if \fIinterp\fR is non-NULL, \fBTcl_OpenFileChannel\fR
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leaves an error message in \fIinterp->result\fR after any error.
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.SH TCL_OPENCOMMANDCHANNEL
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.PP
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\fBTcl_OpenCommandChannel\fR provides a C-level interface to the
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functions of the \fBexec\fR and \fBopen\fR commands.
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It creates a sequence of subprocesses specified
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by the \fIargv\fR and \fIargc\fR arguments and returns a channel that can
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be used to communicate with these subprocesses.
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The \fIflags\fR argument indicates what sort of communication will
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exist with the command pipeline.
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.PP
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If the \fBTCL_STDIN\fR flag is set then the standard input for the
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first subprocess will be tied to the channel: writing to the channel
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will provide input to the subprocess. If \fBTCL_STDIN\fR is not set,
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then standard input for the first subprocess will be the same as this
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application's standard input. If \fBTCL_STDOUT\fR is set then
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standard output from the last subprocess can be read from the channel;
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otherwise it goes to this application's standard output. If
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\fBTCL_STDERR\fR is set, standard error output for all subprocesses is
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returned to the channel and results in an error when the channel is
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closed; otherwise it goes to this application's standard error. If
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\fBTCL_ENFORCE_MODE\fR is not set, then \fIargc\fR and \fIargv\fR can
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redirect the stdio handles to override \fBTCL_STDIN\fR,
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\fBTCL_STDOUT\fR, and \fBTCL_STDERR\fR; if it is set, then it is an
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error for argc and argv to override stdio channels for which
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\fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, and \fBTCL_STDERR\fR have been set.
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.PP
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If an error occurs while opening the channel, \fBTcl_OpenCommandChannel\fR
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returns NULL and records a POSIX error code that can be retrieved with
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\fBTcl_GetErrno\fR.
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In addition, \fBTcl_OpenCommandChannel\fR leaves an error message in
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\fIinterp->result\fR if \fIinterp\fR is not NULL.
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.SH TCL_MAKEFILECHANNEL
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.PP
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\fBTcl_MakeFileChannel\fR makes a \fBTcl_Channel\fR from an existing,
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platform-specific, file handle.
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.SH TCL_GETCHANNEL
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.PP
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\fBTcl_GetChannel\fR returns a channel given the \fIchannelName\fR used to
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create it with \fBTcl_CreateChannel\fR and a pointer to a Tcl interpreter in
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\fIinterp\fR. If a channel by that name is not registered in that interpreter,
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the procedure returns NULL. If the \fImode\fR argument is not NULL, it
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points at an integer variable that will receive an OR-ed combination of
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\fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR describing whether the channel is
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open for reading and writing.
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.SH TCL_REGISTERCHANNEL
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.PP
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\fBTcl_RegisterChannel\fR adds a channel to the set of channels accessible
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in \fIinterp\fR. After this call, Tcl programs executing in that
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interpreter can refer to the channel in input or output operations using the
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name given in the call to \fBTcl_CreateChannel\fR.
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After this call the channel becomes the property of the interpreter.
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The caller should not call \fBTcl_Close\fR for the channel; the
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channel will be closed automatically when it is unregistered from
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the interpreter.
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Furthermore, it is not generally safe to reference the channel
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anymore, since it could be deleted at any time by a \fBclose\fR
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command in the interpreter.
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.SH TCL_UNREGISTERCHANNEL
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.PP
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\fBTcl_UnregisterChannel\fR removes a channel from the set of channels
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accessible in \fIinterp\fR. After this call, Tcl programs will no longer
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be able to use the channel's name to refer to the channel in that
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interpreter. If this operation removed the last registration of the channel
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in any interpreter, the channel is also closed and destroyed.
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.SH TCL_CLOSE
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.PP
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\fBTcl_Close\fR destroys the channel \fIchannel\fR, which must denote a
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currently open channel.
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The channel should not be registered in any interpreter when
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\fBTcl_Close\fR is called; see the manual entry for \fBTcl_CreateChannel\fR
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for a description of \fBTcl_RegisterChannel\fR and \fBTcl_UnregisterChannel\fR.
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Buffered output is flushed to the channel's output device prior to
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destroying the channel, and any buffered input is discarded.
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If this is a blocking channel, the call does not return until all
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buffered data is successfully sent to the channel's output device.
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If this is a nonblocking channel and there is buffered output that
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cannot be written without blocking, the call
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returns immediately; output is flushed in the background and
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the channel will be closed once all of the buffered data has
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been output.
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In this case errors during flushing are not reported.
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.PP
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If the channel was closed successfully, \fBTcl_Close\fR returns \fBTCL_OK\fR.
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If an error occurs, \fBTcl_Close\fR returns \fBTCL_ERROR\fR and records a
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POSIX error code that can be retrieved with \fBTcl_GetErrno\fR.
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If the channel is being closed synchronously and an error occurs during
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closing of the channel and \fIinterp\fR is not NULL, an error message is
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left in \fIinterp->result\fR.
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.PP
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Note: it is not safe to call \fBTcl_Close\fR on a channel that has
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been registered in an interpreter using \fBTcl_RegisterChannel\fR;
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see the documentation for \fBTcl_RegisterChannel\fR for details.
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.SH TCL_READ
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.PP
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\fBTcl_Read\fR consumes up to \fItoRead\fR bytes of data from
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\fIchannel\fR and stores it at \fIbuf\fR.
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The return value of \fBTcl_Read\fR is the number of characters written
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at \fIbuf\fR.
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The buffer produced by \fBTcl_Read\fR is not NULL terminated. Its contents
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are valid from the zeroth position up to and excluding the position
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indicated by the return value.
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If an error occurs, the return value is -1 and \fBTcl_Read\fR records
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a POSIX error code that can be retrieved with \fBTcl_GetErrno\fR.
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.PP
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The return value may be smaller than the value of \fItoRead\fR, indicating
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that less data than requested was available, also called a \fIshort
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read\fR.
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In blocking mode, this can only happen on an end-of-file.
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In nonblocking mode, a short read can also occur if there is not
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enough input currently available: \fBTcl_Read\fR returns a short
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count rather than waiting for more data.
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.PP
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If the channel is in blocking mode, a return value of zero indicates an end
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of file condition. If the channel is in nonblocking mode, a return value of
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zero indicates either that no input is currently available or an end of
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file condition. Use \fBTcl_Eof\fR and \fBTcl_InputBlocked\fR
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to tell which of these conditions actually occurred.
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.PP
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\fBTcl_Read\fR translates platform-specific end-of-line representations
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into the canonical \fB\en\fR internal representation according to the
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current end-of-line recognition mode. End-of-line recognition and the
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various platform-specific modes are described in the manual entry for the
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Tcl \fBfconfigure\fR command.
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.SH TCL_GETS
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.PP
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\fBTcl_Gets\fR reads a line of input from a channel and appends all of
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the characters of the line except for the terminating end-of-line character(s)
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to the dynamic string given by \fIdsPtr\fR.
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The end-of-line character(s) are read and discarded.
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.PP
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If a line was successfully read, the return value is greater than or
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equal to zero, and it indicates the number of characters stored
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in the dynamic string.
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If an error occurs, \fBTcl_Gets\fR returns -1 and records a POSIX error
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code that can be retrieved with \fBTcl_GetErrno\fR.
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\fBTcl_Gets\fR also returns -1 if the end of the file is reached;
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the \fBTcl_Eof\fR procedure can be used to distinguish an error
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from an end-of-file condition.
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.PP
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If the channel is in nonblocking mode, the return value can also
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be -1 if no data was available or the data that was available
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did not contain an end-of-line character.
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When -1 is returned, the \fBTcl_InputBlocked\fR procedure may be
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invoked to determine if the channel is blocked because of input
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unavailability.
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.SH TCL_WRITE
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.PP
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\fBTcl_Write\fR accepts \fItoWrite\fR bytes of data at \fIbuf\fR for output
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on \fIchannel\fR. This data may not appear on the output device
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immediately. If the data should appear immediately, call \fBTcl_Flush\fR
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after the call to \fBTcl_Write\fR, or set the \fB-buffering\fR option on
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the channel to \fBnone\fR. If you wish the data to appear as soon as an end
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of line is accepted for output, set the \fB\-buffering\fR option on the
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channel to \fBline\fR mode.
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.PP
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The \fItoWrite\fR argument specifies how many bytes of data are provided in
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the \fIbuf\fR argument. If it is negative, \fBTcl_Write\fR expects the data
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to be NULL terminated and it outputs everything up to the NULL.
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.PP
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The return value of \fBTcl_Write\fR is a count of how many
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characters were accepted for output to the channel. This is either equal to
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\fItoWrite\fR or -1 to indicate that an error occurred.
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If an error occurs, \fBTcl_Write\fR also records a POSIX error code
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that may be retrieved with \fBTcl_GetErrno\fR.
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.PP
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Newline characters in the output data are translated to platform-specific
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end-of-line sequences according to the \fB\-translation\fR option for
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the channel.
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.SH TCL_FLUSH
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.PP
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\fBTcl_Flush\fR causes all of the buffered output data for \fIchannel\fR
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to be written to its underlying file or device as soon as possible.
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If the channel is in blocking mode, the call does not return until
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all the buffered data has been sent to the channel or some error occurred.
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The call returns immediately if the channel is nonblocking; it starts
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a background flush that will write the buffered data to the channel
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eventually, as fast as the channel is able to absorb it.
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.PP
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The return value is normally \fBTCL_OK\fR.
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If an error occurs, \fBTcl_Flush\fR returns \fBTCL_ERROR\fR and
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records a POSIX error code that can be retrieved with \fBTcl_GetErrno\fR.
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.SH TCL_SEEK
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.PP
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\fBTcl_Seek\fR moves the access point in \fIchannel\fR where subsequent
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data will be read or written. Buffered output is flushed to the channel and
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buffered input is discarded, prior to the seek operation.
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.PP
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\fBTcl_Seek\fR normally returns the new access point.
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If an error occurs, \fBTcl_Seek\fR returns -1 and records a POSIX error
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code that can be retrieved with \fBTcl_GetErrno\fR.
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After an error, the access point may or may not have been moved.
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.SH TCL_TELL
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.PP
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\fBTcl_Tell\fR returns the current access point for a channel. The returned
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value is -1 if the channel does not support seeking.
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.SH TCL_GETCHANNELOPTION
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.PP
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\fBTcl_GetChannelOption\fR retrieves, in \fIdsPtr\fR, the value of one of
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the options currently in effect for a channel, or a list of all options and
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their values. The \fIchannel\fR argument identifies the channel for which
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to query an option or retrieve all options and their values.
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If \fIoptionName\fR is not NULL, it is the name of the
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option to query; the option's value is copied to the Tcl dynamic string
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denoted by \fIoptionValue\fR. If
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\fIoptionName\fR is NULL, the function stores an alternating list of option
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names and their values in \fIoptionValue\fR, using a series of calls to
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\fBTcl_DStringAppendElement\fR. The various preexisting options and
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their possible values are described in the manual entry for the Tcl
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\fBfconfigure\fR command. Other options can be added by each channel type.
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These channel type specific options are described in the manual entry for
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the Tcl command that creates a channel of that type; for example, the
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additional options for TCP based channels are described in the manual entry
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for the Tcl \fBsocket\fR command.
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The procedure normally returns \fBTCL_OK\fR. If an error occurs, it returns
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\fBTCL_ERROR\fR and calls \fBTcl_SetErrno\fR to store an appropriate POSIX
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error code.
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.SH TCL_SETCHANNELOPTION
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.PP
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\fBTcl_SetChannelOption\fR sets a new value for an option on \fIchannel\fR.
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\fIOptionName\fR is the option to set and \fInewValue\fR is the value to
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set.
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The procedure normally returns \fBTCL_OK\fR. If an error occurs,
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it returns \fBTCL_ERROR\fR; in addition, if \fIinterp\fR is non-NULL,
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\fBTcl_SetChannelOption\fR leaves an error message in \fIinterp->result\fR.
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.SH TCL_EOF
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.PP
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\fBTcl_Eof\fR returns a nonzero value if \fIchannel\fR encountered
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an end of file during the last input operation.
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.SH TCL_INPUTBLOCKED
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.PP
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\fBTcl_InputBlocked\fR returns a nonzero value if \fIchannel\fR is in
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nonblocking mode and the last input operation returned less data than
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requested because there was insufficient data available.
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The call always returns zero if the channel is in blocking mode.
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.SH TCL_INPUTBUFFERED
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.PP
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\fBTcl_InputBuffered\fR returns the number of bytes of input currently
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buffered in the internal buffers for a channel. If the channel is not open
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for reading, this function always returns zero.
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.SH "SEE ALSO"
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DString(3), fconfigure(n), filename(n), fopen(2), Tcl_CreateChannel(3)
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.SH KEYWORDS
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access point, blocking, buffered I/O, channel, channel driver, end of file,
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flush, input, nonblocking, output, read, seek, write
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