On 2020-04-25, Mark D. Baushke <mdb@xxxxxxxxxxx> wrote: > Hi Michael, Hi Mark, > Using POSIX command-line semantics is a fine goal. Someone might drop > the backward-compatiblity of the commands and then things would begin to > break. Indeed, that's what motivated the patch. The version of tail on my system does not support the legacy options. > However, there is an alternative. Do not use these POSIX commands > that have changed their command-line syntax if one that exists and is > more stable is also available. > >> @@ -353,7 +353,7 @@ depend-rebuild: >> rm -f config.h >> touch config.h >> makedepend -w1000 -Y. -f .depend *.c 2>/dev/null >> - (head -2 .depend; tail +3 .depend | sort) >.depend.tmp >> + (head -n 2 .depend; tail -n +3 .depend | sort) >.depend.tmp >> mv .depend.tmp .depend >> rm -f config.h > > I am speaking of the use of 'sed' which has been pretty stable since at > least 1992 and mostly the same going back to 1974. > > Using sed for compatibility with all possible portable releases seems > 'better' to me than just upgrading a command because POSIX thinks it is > a good idea. This seems like a fine option to me. > For example: > > head -2 == head -n 2 == sed 'n;q' Another possibility is `sed 2q`, which works for any number. It's even mentioned in the rationale section as a way to simulate head(1). > tail +3 == tail -n +3 == sed '1,2d' > > The sed program has been around a lot longer without these command-line > semantics changing for POSIX. > > These idioms should work fine going back to at least the BSD version of > sed from 1992 by Diomidis Spinellis and maybe even going back to Lee E. > McMahon's version in 1974. > > @@ -353,7 +353,7 @@ depend-rebuild: > rm -f config.h > touch config.h > makedepend -w1000 -Y. -f .depend *.c 2>/dev/null > - (head -2 .depend; tail +3 .depend | sort) >.depend.tmp > + (sed 'n;q' .depend; sed '1,2d' .depend | sort) >.depend.tmp > mv .depend.tmp .depend > rm -f config.h > > The idea of the OpenSSH portable release is to be portable across a LOT > of UNIX (and even some non-UNIX releases). If that is the goal, why > enforce the need to fetch and build POSIX-compliant versions of head and > tail for very old systems? I think this script is only necessary to rebuild the .depend file, which is not usually necessary, but you make a good point. I didn't realize that some implementations did not support the -n option. The change you suggested sounds good to me. -Michael _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
