Bash exit codes: 0, 1, 2, 126, 127, 128+n and 255

Every command returns an exit status from 0 to 255; $? holds the status of the last command. 0 means success and any other value means failure. bash reserves a few values: 126 (found but not executable), 127 (command not found) and 128 + n (terminated by signal n).

Exit code table

Read the exit status

true; echo "true -> $?"
false; echo "false -> $?"
grep -q needle <<< "haystack"; echo "grep without match -> $?"
nonexistent-tool 2>/dev/null; echo "not found -> $?"
(exit 300); echo "exit 300 -> $?"

true -> 0
false -> 1
grep without match -> 1
not found -> 127
exit 300 -> 44

Values above 255 wrap modulo 256, so exit 300 returns 44.

Signals: 128 + n

When a process is killed by a signal, bash reports 128 plus the signal number. Common values on Linux: