Passphrase from external program, script, or batch file

Johan Wevers
Wed, 6 Dec 2000 00:07:10 +0100 (MET)

Marcus wrote:

> I saw something like --passphrase-fd in the archive, but I don't
> understand what it means or is really doing. Can anybody explain?
A file descriptor is an even more low-level function than a file. They are represented by numbers, 0 = standard input, 1 = standard output and 2 = standard error (on DOS, stderr == stdout, NT follows the unix convention here). However, you can also open higher numbers. If you have opened such an fd, you can send data through it via something that is called a pipe. One end sends data, the other end reads it (for 2-way communication you'll have to open 2 fd's). Opening a fd and a pipe to send data through it are standard methods in many programming languages, including C and perl. More information about fd's can be found in K&R chapter 8, and for piping through an fd I have some example code in C (unix specific I'm affraid, but the piping might also work in windows) if you're interested (a program I once wrote to communicate this way with pgp 2.6.3). -- ir. J.C.A. Wevers // Physics and science fiction site: // PGP/GPG public keys at -- Archive is at - Unsubscribe by sending mail with a subject of "unsubscribe" to