exit() status and main() return code
Per ANSI C and POSIX:
| Value | Symbol | Description |
|---|---|---|
| 0 | EXIT_SUCCESS |
Program terminated successfully |
| 1 | EXIT_FAILURE |
Program terminated unsuccessfully |
| 2 | Usage (command line syntax) error | |
| 3 to 125 | Other failure, implementation/program defined | |
| 126 | Not executable | |
| 127 | Command not found | |
| 128 to 255 | Terminated by signal; Return code is signo+128 |
NOTE: Only 8 bits of the status value are used, even though the values are declared as int.