A file descriptor is a number which specifies a IO stream. In Unix and other POSIX environments, there is an array called the file descriptor table, and you can use a number which indexes one of those entries: 0 is STDIN, 1 is STDOUT, 2 is STDERR ... the remainder you open yourself.

See Wikipedia's explanation.

As Occam said: Entia non sunt multiplicanda praeter necessitatem.

In reply to Re^3: Difference between File Handles and File Descriptors in function parameters. by TomDLux
in thread Difference between File Handles and File Descriptors in function parameters. by tusty

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