El Miércoles 03/02/2016, Warren Young escribió: > On Feb 3, 2016, at 8:57 AM, m.roth at 5-cent.us wrote: > > Notice the *deeply* weird syntax of "=-<cmd>”. > > That syntax comes from make(1), where it means the same thing. make(1) has > been with us since 1977, so I’d think “old and familiar” is a better > description than “deeply weird.” > > > And, I read in the manpage for systemd.service that if you precede it > > with an @, it will pass arguments. Why it does not use the > > used-everywhere-else of *post*fixing those parms, I have no data. > > You’ve misread the page. > > All this option does is lets you run one command but tell the command > itself that it was called by a different name. I’m not sure why the > systemd creators added this, since you normally get this behavior with > links: > > $ sudo yum install unzip > $ ls -li /bin/unzip /bin/infozip > 135096149 -rwxr-xr-x. 2 root root 181248 Mar 18 2015 unzip > 135096149 -rwxr-xr-x. 2 root root 181248 Mar 18 2015 zipinfo > > That is, we have a single program binary with two different names. > Invoking the program as “zipinfo” makes it behave differently than if you > invoke it as “unzip”. > > All this systemd feature does is lets you say something like: > > ExecStart=@/bin/unzip zipinfo ... > > That is, you can run the unzip binary but *call it* zipinfo. > > Again, I don’t know why they couldn’t just do it with links. However, I > will point out that the C programming interfaces on your system (execv() > and friends) also support this feature, and have since back before 1977, so > that this, too, is not some fresh new weirdness. I guess that's probably to execute scripts and "hide" the name of the interpreter, e.g.: ExecStart=@/usr/bin/python my_cool_service --my_args > > I also don't > > understand why you'd set as an out-of-the-box default that it should fail > > to come up if it can't resolve any export host, rather than default to > > coming up. > > You do it for the same reason you’d fail when mounting any other > filesystem. It may be critical to operation, as with shared /usr. -- Ricardo J. Barberis Usuario Linux Nº 250625: http://counter.li.org/ Usuario LFS Nº 5121: http://www.linuxfromscratch.org/ Senior SysAdmin / IT Architect - www.DonWeb.com