Exit Codes
1 Catchall for general errors let "var1 = 1/0" Miscellaneous errors, such as "divide by zero" and other impermissible operations
2 Misuse of shell builtins (according to Bash documentation) empty_function() {} Missing keyword or command, or permission problem (and diff return code on a failed binary file comparison).
126 Command invoked cannot execute /dev/null Permission problem or command is not an executable
127 "command not found" illegal_command Possible problem with $PATH or a typo
128 Invalid argument to exit exit 3.14159 exit takes only integer args in the range 0 - 255 (see first footnote)
128+n Fatal error signal "n" kill -9 $PPID of script $? returns 137 (128 + 9)
130 Script terminated by Control-C Ctl-C Control-C is fatal error signal 2, (130 = 128 + 2, see above)
255* Exit status out of range exit -1 exit takes only integer args in the range 0 - 255