Unix

fork() is a system call that is used for process creation. The calling process first creates a copy of itself (i.e. the child process) which may be followed by a call to exec().
fork() may fail and returns -1 in that case.
When calling kill(), first check if your pid is valid. If you treat -1 as a valid pid, you're going to kill all processes "for which the calling process has permission to send signals, except for process 1 (init)".

Bash

If you see the error message /bin/sh^M: bad interpreter, your file has DOS line endings (CRLF) and must thus be converted to Unix line endings (LF) first.

$ dig whoami.ds.akahelp.net TXT +short
# or
$ dig whoami.akamai.net A +short