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  • thanks for pointing the header file.. tried looking into the documentation of a few utils.. hard time finding the exit codes, seems most will be the stderrs... Commented Jan 22, 2014 at 9:13
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    errno.h is irrelevant when it comes to exit codes, only error messages. Commented Jan 22, 2014 at 23:41
  • Most programs return exit codes according to the BSD convention, as laid out in sysexits.h. However, some programs do return errnos, and I actually think returning errnos makes the most sense. Unhandled errnos propagate upwards, like exceptions, (the errno stays, functions return e.g., -1 or 0|NULL). Since programs are just functions, albeit functions that are run in a separate address space, it makes sense that a program might wish to continue the errno propagation across the process boundary. Commented Jan 12, 2016 at 0:14
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    @PSkocik, do you have an example of such a command? errnos are not portable (values not consistent across systems), and there's no portable way to get the err name or message from the value (zsh has a builtin for that). Not to mention that some systems have errnos above 123 that would clash with common special-meaning error codes. Usually, commands print the messages from the errno and return a success/failure exit status. commands are intended for users. functions/system calls are intended for programmers. Commented Sep 7, 2016 at 8:17
  • @StéphaneChazelas I've seen it a couple of times, but not in any well established programs, I have to admit. I've been personally returning errno+1 in my toy system lately ( so that 1 continues to mean "any error") because I think serializing errno's across the process boundary makes better sense than translating according to the BSD convention, as program executions are essentially function invocations, and functions use errno. I use my own last-exit-status decoder in my PROMPT_COMMAND (bash) so I get something like "($numeric_code|$bsd_decoded|$errno_plus_one_decoded)". Commented Sep 7, 2016 at 9:00