Hi, Am 09.08.2015 um 17:04 schrieb Santiago Vila: > Hello. > > [ Apologies if this is a FAQ ]. > > Debian has recently switched the "mesg" implementation from > the one in sysvinit to the one in util-linux. > > We have found a subtle issue: The old mesg didn't have any error codes > at all. The new mesg (from util-linux) has the following error codes: > > 0 Messages are allowed. > > 1 Messages are not allowed. > >> 1 An error has occurred. > The problem is that those error codes are in effect not only when > the mesg command is invoked alone: > > mesg > > but also when it's used with an argument: > > mesg y > mesg n > > This breaks the default /root/.profile which has a simple "mesg n" at The profile is usually sourced. How does the error show up at the login prompt on Debian? -- Reuti > the end, so we will probably have to hide the error like this: > > mesg n || true > > but this is a little bit weird and I wonder how much people will have > to do this as well. > > In Unix, usually, whenever I tell a command to do something, there is > only an error when the command is not able to do what I ask it to do. > > In this case, however, the "mesg n" is succesful, as it is actually > able to disable write to the terminal, and yet it exits with an error. > > I think this does not make much sense and would humbly propose that > the behaviour is changed so that error codes are only used when > the mesg is used alone, without any arguments. > > Surely that a change like this might in theory break some scripts, > but let's see what kind of breakage we could expect: > > * People who write this: > > mesg y > > will not need to change anything. > > * People who write this: > > mesg n || true > > will finally be able to remove the "|| true" part. If they don't > remove the "|| true" part, nothing really bad will happen. > > In fact, this could even improve things a little bit, as "mesg" alone > will fail if the mesg does not exist. > > * People writing things like this: > > if mesg 2> /dev/null; then > echo mesg is y > else > echo mesg is n > fi > > which is where exit codes are actually useful, will not be affected at > all. > > Of course one can always create a complex use case where a change in > exit codes would break the script, but I think those would be a very > small minority. > > So: Would you please consider a change in mesg behaviour regarding > exit codes, so that "mesg n" does not gratuitously fail? > > Thanks. > -- > To unsubscribe from this list: send the line "unsubscribe util-linux" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe util-linux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
