int fd = socket(//arguments);
Can this descriptor be passed to another process via IPC and still be valid or is it local to the process that created it?
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Jonathan Leffler
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Alon
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1If it were global, how could different processes use the same descriptor numbers for the standard streams? – Dmitri Feb 18 '17 at 18:56
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You are right I forgot that. Stupid question. – Alon Feb 18 '17 at 18:56
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File descriptors are local to the process. For instance, every process will have its standard input, output, and error on file descriptors 0, 1, and 2.
It is possible to pass a file descriptor to another process over a UNIX domain socket. When this is done, each process will have a copy of the file descriptor, possibly under a different FD number. It's a kind of messy API, though, and is rarely used.
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Yes, file descriptors are local to the process. When a process forks a child, however, the parent and child have the same file descriptor table. This is great because it allows for IO redirection, which is a pretty handy trick.
Brandon Busby
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