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Top Forums Programming Very simple Unix Prog in C, could use advice/help Post 17210 by AtleRamsli on Tuesday 12th of March 2002 07:55:31 AM
Old 03-12-2002
Excellent comment about the race condition!

One thing puzzles me, this code looks C++-ish?
Are // accepted as C comments, now?

Anyway, what I wanted to add, was that even though there is no _syntactical_ distinction between 'Procedure' and 'Function' in C, the _semantic_ one remains! So, unless a function returns void (the Function is not a "Function" but a "Procedure" Smilie ) its return value must always be checked.
This is why Perderabo tells you that 'it's ok to check first, but you must check after'

I have a 'standard' way for dealing with opening/creation.

/*
Try to open, if that fails, _try_to_ create.
If create was successful, close.
Now, we have done what we can to make sure
we can open the file, so now try to open
and return the result.
*/
myopen(...)
{
if (fd = open(...) == -1) {
if (fd = creat(...) != -1)
close(fd);
fd = open(...);
}
return(fd);
}

It all depends on what you define to be an '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. SEE ALSO
file(n), open(n), socket(n), eof(n), Tcl_StandardChannels(3) KEYWORDS
blocking, channel, close, nonblocking Tcl 7.5 close(n)

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