On Tue, Jun 13, 2017 at 3:52 PM, Rob Landley <r...@landley.net> wrote: > On 06/12/2017 10:49 AM, enh wrote: >> On Sat, Jun 10, 2017 at 11:29 AM, Rob Landley <r...@landley.net> wrote: >>> Would it be useful if perror_exit() set exitval to errno by default >>> instead of 1? They're well defined values that let you know _what_ happened. >> >> ...except the caller doesn't know whether it's looking at an errno >> value. and what could a caller realistically do anyway? it's bad >> enough working out what exactly EINVAL means if the last thing you did >> was call mmap, but if you just ran toybox... that failure could be >> coming from anywhere. > > It's nonzero, and 99% of the time _all_ we're saying with the exit code > is "it's nonzero".
(i think we're in violent agreement at this point, but two other things that occurred to me...) except when it's 0 because we've called perror_exit on something that didn't actually set errno. i'm sure i haven't seen "something went wrong: Success" for the last time! and some errno values are too large for an exit status: mips in particular has plenty of errno values that would look like signals (useful ones like ETIMEDOUT, even), and EDQUOT manages to be as high as 1133. > Right now it's providing the errno info in human readable format via > perror_exit(), and if a script really wants to know it can... parse the > string and hope nobody ever changes the locale? I guess that's the best > we can do. :P > >>> I just fixed grep so it doesn't error_exit() when it hits a dangling >>> symlink (because fdopen() failed to covert fd to file *), but >>> perror_msg() sets errno to 1, and "grep -rq blah" has 1 mean "didn't >>> find what we were grepping for". In this instance, finding it stops and >>> returns 0 immediately so if you hit one of those it won't change the >>> results, but the caller can't distinguish "did not find" from "hit >>> dangling symlink and wanted to report it as an error" unless they >>> capture stderr. In this case that's probably fine, but it made me think >>> about the more general problem. >> >> isn't grep a well-known special case? > > Not according to posix? > > http://pubs.opengroup.org/onlinepubs/9699919799/utilities/grep.html > >> "if any error occurs and -q is not given, the exit status is 2." > > https://xkcd.com/221/ > > Posix just says >1 for error, which A) I don't think I've implemented > yet, B) would argue against the errno approach because 1 is EPERM and > that's a commonish failure: > > $ ./ls /root > ls: /root: Permission denied > > That said, I can make grep _start_ returning 2 for errors. I still have > to do --color before you can use the toybox one. (Did 90% of it once and > got distracted for a month then lost it to a "git clean -fdx && git > checkout -f" in the wrong directory. As usual.) > >>> The downside would be other commands that use error return values other >>> than 0 and 1 already. This could create false positives for that. >> >> i've certainly seen scripts explicitly check for 0 and 1 exit statuses. > > I was thinking "cmp", which is _currently_ doing the 0 1 or 2 thing. :) > > Hmmm... that sort of implies perror_exit() should set errno to 2 instead > of setting it to 1? But again, a potentially intrustive change so > probably not. > >>> *shrug* Thought I'd ask. I still have this annoying cold and trying to >>> think through it myself right now isn't getting a lot of traction. >> >> seems to me like it would break a lot of expectations, while not being >> obviously usable? > > Yeah, I couldn't quite see the way to make proper use of this > information either. I thought that might be because I'm under the > weather, but if nobody else is seeing one... > > It's probably one of those things where if toybox had done it from the > start, it'd be fine, but as the installed base grows the cost of changes > to existing commands gets higher. :P > > Rob > > P.S. I an wrestling with your help text processing issue as we speak, > hope to have the fix checked in today. And THEN I can cut the release... > _______________________________________________ > Toybox mailing list > Toybox@lists.landley.net > http://lists.landley.net/listinfo.cgi/toybox-landley.net -- Elliott Hughes - http://who/enh - http://jessies.org/~enh/ Android native code/tools questions? Mail me/drop by/add me as a reviewer. _______________________________________________ Toybox mailing list Toybox@lists.landley.net http://lists.landley.net/listinfo.cgi/toybox-landley.net
