12-24-2001
I don't know any portable way for a process to find out the number of files it has open.
But consider this case...I open 16 files and allocate fd 0 through fd 15. Then I close fd 0 through fd 14. This leaves only fd 15 open. If you could magically find out that only one file is open, how would that help you? You still don't know which fd to close.
The shell will allocate fd 0, 1, and 2 and pass these to you. Your program should keep track of which files it opens.
If you have lost track of want files are open, the only thing I can suggest to do a getrlimit() to obtain the highest possible fd that could ever be allocated. Then close all possible fd's. The close call will fail if the file is not open, so you just ignore that error.
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close(n) Tcl Built-In Commands close(n)
__________________________________________________________________________________________________________________________________________________
NAME
close - Close an open channel
SYNOPSIS
close channelId
_________________________________________________________________
DESCRIPTION
Closes the channel given by channelId.
ChannelId must be an identifier for an open channel such as a Tcl standard channel (stdin, stdout, or stderr), the return value from an
invocation of open or socket, or the result of a channel creation command provided by a Tcl extension.
All buffered output is flushed to the channel's output device, any buffered input is discarded, the underlying file or device is closed,
and channelId becomes unavailable for use.
If the channel is blocking, the command does not return until all output is flushed. If the channel is nonblocking and there is unflushed
output, the channel remains open and the command returns immediately; output will be flushed in the background and the channel will be
closed when all the flushing is complete.
If channelId is a blocking channel for a command pipeline then close waits for the child processes to complete.
If the channel is shared between interpreters, then close makes channelId unavailable in the invoking interpreter but has no other effect
until all of the sharing interpreters have closed the channel. When the last interpreter in which the channel is registered invokes close,
the cleanup actions described above occur. See the interp command for a description of channel sharing.
Channels are automatically closed when an interpreter is destroyed and when the process exits. Channels are switched to blocking mode, to
ensure that all output is correctly flushed before the process exits.
The command returns an empty string, and may generate an error if an error occurs while flushing output. If a command in a command pipe-
line created with open returns an error, close generates an error (similar to the exec command.)
EXAMPLE
This illustrates how you can use Tcl to ensure that files get closed even when errors happen by combining catch, close and return:
proc withOpenFile {filename channelVar script} {
upvar 1 $channelVar chan
set chan [open $filename]
catch {
uplevel 1 $script
} result options
close $chan
return -options $options $result
}
SEE ALSO
file(n), open(n), socket(n), eof(n), Tcl_StandardChannels(3)
KEYWORDS
blocking, channel, close, nonblocking
Tcl 7.5 close(n)