On 08/19/2013 07:51 PM, Guan Nan Ren wrote: >> This treats '-' as an unrecognized option (which is a bit misleading, >> since in POSIX terminology a lone - is NOT an option but an argument). >> It also raises the question - should we allow for an XMLFILE of '-' to >> mean reading from stdin, the way POSIX recommends? That is, should we >> support: >> >> virsh dumpxml $dom | virt-xml-validate - > > > grep use "grep -f -" to donate the standard input. As written in its manpage > -f is specified by POSIX. If we use -f, the single hyphen can be used > as a filename. But as you said in the follow, user can prefix the filename > with a path - ./-, or /home/Tim/-, so it is still fine in this case. Actually, 'grep -f - file' and 'grep pattern -' are two quite different uses of '-' meaning stdin (one treats stdin as the file containing the pattern, the other treats stdin as the file to search). But yes, the point is that since POSIX requires '-' to mean stdin when possible, people are used to that idiom, and used to using ./- when wanting to refer to a file literally named -. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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