negative exit codes?

wscott44 has asked for the wisdom of the Perl Monks concerning the following question:

Hi Folks: Why is it difficult to return a negative exit code to the UNIX Korn shell (on AIX) and see it as I expect it? /tmp> perl -e 'exit -2' ; echo $? 254 /tmp> perl -e 'exit -1' ; echo $? 255 /tmp> perl -e 'exit -111' ; echo $? 145 /tmp> perl -e 'exit -123' ; echo $? 133 Thank you, Wayne

Comment on negative exit codes?

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Re: negative exit codes? by almut (Canon) on Jun 05, 2008 at 21:11 UTC
Unix is using an 8-bit value as exit/return code (see `man wait`). This value is typically interpreted as an unsigned value by the shell. Update: but you could use Perl to display it properly :) For example `$ perl -e 'exit -111' $ perl -e "print unpack('c',pack 'C', $?),\$/" -111` [download] (possible range -128 .. 127)	[reply] [d/l] [select]
Re^2: negative exit codes? by wscott44 (Initiate) on Jun 06, 2008 at 13:46 UTC
Thank you to those who replied so promptly. It's all clearer now. As for using Perl to display it properly... that's what I thought :-D Regards, Wayne	[reply]
Re: negative exit codes? by pc88mxer (Vicar) on Jun 05, 2008 at 21:07 UTC
I am pretty sure exit status codes are limited to 8 bits -- see this Wikipedia article: Exit status That's why a status of -1 is showing up as 255. Trying this: `bash -c 'exit -1'` produces the error `Illegal number: -1`, so I doubt status codes are meant to be interpreted as signed integers.	[reply] [d/l] [select]