At work, I have some neat-o install scripts that generate other scripts containing configuration values. At one point, three of these scripts output to stderr by echo’ing to /proc/self/2 (2 == stderr). These are messages I want to be visible to the user even if they are redirecting stdout to a file. Strangely, it works for me, but not for other people who are installing it. They get: “/proc/self/2: Permission denied".
These “other people” are support and testing staff, and they log into Linux system using ‘personal’ IDs, then use sudo su - XXXadmin, which is what we call a ‘functional’ ID. The directory entries at /proc/*/fd/* are owned by the first user, with permissions of (0620)
crw--w---- 1 tim tty 136, 8 Apr 9 15:58 /proc/self/fd/2
But when the user does sudo su – XXXadmin, the ownership of /proc/self/fd/2 is still the original owner, and so XXXadmin can’t write to this ‘file’.
Long story short: I couldn’t find any bash-isms that allow echo to be redirected to file-descriptor 2 directly, so I ended up replacing the echo statement with a perl script
perl -e 'print STDERR "message\n";'
Not really happy forking an entire interpreter just to write a little message to stderr, but maybe someday I’ll stumble across a better way.
