parsing the way getopt(3) would, if only it could handle the (required)
-signumber and -signame options. This adds two "features" to kill,
-ssigname and -lstatus now work (ie: one word with all of the '-', the
option letter, and its value) and "--" also now works (kill -- -pid1 pid2
will not attempt to send the pid1 signal to pid2, but rather SIGTERM
to the pid1 process group and pid2). It is still the case that (apart
from --) at most 1 option is permitted (-l, -s, -signame, or -signumber.)
Note that we now have an ambiguity, -sname might mean "-s name" or
send the signal "sname" - if one of those turns out to be valid, that
will be accepted, otherwise the error message will indicate that "sname"
is not a valid signal name, not that "name" is not. Keeping the "-s"
and signal name as separate words avoids this issue.
Also caution: should someone be weird enough to define a new signal
name (as in the part after SIG) which is almost the same name as an
existing name that starts with 'S' by adding an extra 'S' prepended
(eg: adding a SIGSSYS) then the ambiguity problem becomes much worse.
In that case "kill -ssys" will be resolved in favour of the "-s"
flag being used (the more modern syntax) and would send a SIGSYS, rather
that a SIGSSYS. So don't do that.
While here, switch to using signalname(3) (bye bye NSIG, et. al.), add
some constipation, and show a little pride in formatting the signal names
for "kill -l" (and in the usage when appropriate -- same routine.) Respect
COLUMNS (POSIX XBD 8.3) as primary specification of the width (terminal width,
not number of columns to print) for kill -l, a very small value for COLUMNS
will cause kill -l output to list signals one per line, a very large
value will cause them all to be listed on one line.) (eg: "COLUMNS=1 kill -l")
TODO: the signal printing for "trap -l" and that for "kill -l"
should be switched to use a common routine (for the sh builtin versions.)
All changes of relevance here are to bin/kill - the (minor) changes to bin/sh
are only to properly expose the builtin version of getenv(3) so the builtin
version of kill can use it (ie: make its prototype available.)
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