Show help screen if run from shell

[kevinreddot]

If accidentaly started by a logged-in user, forsh will log it as login attempt. It should detect this and just print help message.

[kevinreddot]

The approach might be to detect if SSH_CONNECTION environment variable is set and parent process of forsh is sshd.

For FreeBSD, seems I need to use kvm_getargv90 to find the process name after the getppid(): https://www.freebsd.org/cgi/man.cgi?query=kvm_getprocs&sektion=3&n=1

For Linux, apparently, the only way is to read /proc directly.

[kevinreddot]

Example of process tree of a program when run via ForceCommand:

13437 - /usr/local/bin/get_ppid_and_name
 13436 - sshd: sss@pts/5
 13423 - sshd: sss [priv]
   842 - /usr/sbin/sshd
     1 - /sbin/init

[kevinreddot]

Wonder, how to do it in a cross-platform way. Also, if run in chroot, /proc might not be available.