Re: Looking for a simple multiprocess-enabled logging module

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Re^2: Looking for a simple multiprocess-enabled logging module by ikegami (Patriarch) on Dec 20, 2004 at 16:17 UTC
I thought that was only true if the string is smaller than a certain size?	[reply]
Re^3: Looking for a simple multiprocess-enabled logging module by tmoertel (Chaplain) on Dec 20, 2004 at 16:47 UTC
On a Unix and equivalent systems if the file you are writing to was opened with the `O_APPEND` flag, writes are guaranteed to be atomic regardless of size, unless the file is a pipe or FIFO, in which case atomicity is guaranteed only if the write size is `PIPE_BUF` or fewer bytes in length. So sayeth the Single Unix Specification on the `write` system call: If the `O_APPEND` flag of the file status flags is set, the file offset shall be set to the end of the file prior to each write and no intervening file modification operation shall occur between changing the file offset and the write operation.... Write requests to a pipe or FIFO shall be handled in the same way as a regular file with the following exceptions: ... Write requests of `PIPE_BUF` bytes or less shall not be interleaved with data from other processes doing writes on the same pipe. Writes of greater than `PIPE_BUF` bytes may have data interleaved, on arbitrary boundaries, with writes by other processes, whether or not the `O_NONBLOCK` flag of the file status flags is set. On most Linux systems, `PIPE_BUF` is 4096. See the `write`(2) man page on your system and the Single Unix Specification for more. Tom Moertel : Blog / Talks / CPAN / LectroTest / PXSL / Coffee / Movie Rating Decoder	[reply]


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