On 04/17/2015 01:05 PM, Peng Yu wrote: >>> If I don't know the number of fields, but I want to sort according to >>> all fields (from 1 to whatever the max number of fields), is there a >>> way to do it? >> >> No one has really asked for that before. Are you going to propose some >> possible extension syntax to make it obvious how to generate as many key >> specifications as necessary to fully cover an arbitrary number of fields >> in a line? > > Since no -k options means treat each line just a whole string, maybe > one can allow -k without specifying any columns as treating each line > as all the set of fields in that line?
Sadly, it is not backwards-compatible to convert an option with mandatory argument into an option with optional argument. By your proposal, 'sort -k1' would be unambiguous, but 'sort -k 1' would be ambiguous as to whether it is 'use field 1 to the end of the line as the only sort key, with stdin as input' (existing meaning) or 'sort by an infinite number of keys, one per field, with ./1 as input' (new meaning). You'd have to burn a new option, maybe spelled -K, to get new semantics. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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