Can someone tell me why this does not work? I'm playing around with file descriptors, but feel a little lost.
#!/bin/bash
echo "This"
echo "is" >&2
echo "a" >&3
echo "test." >&4
The first three lines run fine, but the last two error out. Why?
File descriptors 0, 1 and 2 are for stdin, stdout and stderr respectively.
File descriptors 3, 4, .. 9 are for additional files. In order to use them, you need to open them first. For example:
exec 3<> /tmp/foo #open fd 3.
echo "test" >&3
exec 3>&- #close fd 3.
For more information take a look at Advanced Bash-Scripting Guide: Chapter 20. I/O Redirection.