On 06/04/2015 02:17 PM, Nick Bowler wrote: > Do these problematic shells properly handle: > > for arg > do > ... > done > > when $# is 0?
Yes; all shells do. $ /bin/sh -c 'echo $#; for arg do echo hi; done; echo bye' 0 bye > > If so, can we use the following as a workaround? > > set x words-that-might-expand-to-nothing; shift > for arg > do > ... > done Not ideal, when there are shorter invocations that can do the same. And it's not the expand-to-nothing that is a problem, it is the actual omission: $ /bin/sh -c 'for a in ; do :; done' /bin/sh: syntax error at line 1: `;' unexpected $ /bin/sh -c 'for a in $nothing; do :; done' $ so anything that expands in shell to nothing (whether $nothing, ``, or use of a shell variable rather than a make variable) is fine; the problem is most common in Makefiles where make variables are expanded before the shell sees anything. > > I suppose that might be hard to do in this /particular/ case, as it > looks like the error is coming from a make rule. The Autoconf manual > quite emphatically says to avoid 'for arg; do ...' by using a newline > instead of a semicolon, a feat which is not easily done in make rules. The manual also has a workaround for getting a literal newline in make rules: nlinit=`echo 'nl="'; echo '"'`; eval "$$nlinit" although that only gives you $nl containing newline, and you'd still need another layer of 'eval' if you wanted to actually write the makefile fragment to interpret the newline as a separator between the var-name and 'do'. So yeah, it's not worth it. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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