On Sat, Aug 12, 2006 at 01:51:12AM -0600, Bob Proulx wrote: > Stephane Chazelas wrote: > > [ -e "$cmd" ] || cmd=$(command -v -- "$cmd") || exit > > Bob Proulx wrote: > > > Of course using command as you have done will work for bash. > > > > "command" is a POSIX command. So will work with every POSIX and > > therefore every Unix conformant sh. > > That is not strictly true. While 'command' is POSIX 'command -v' > is actually an optional extension. A system only claiming POSIX > conformance need not implement 'command -v'. See the online standards > documents for more information. > > http://www.opengroup.org/onlinepubs/009695399/utilities/command.html
You're right. command -v is not required by POSIX, but required by Unix (XSI). A lot of shells (like bash) are only POSIX conformant. > And in fact the FreeBSD /bin/sh (among others) implements 'command' > but not 'command -v'. So in practice it is not as portable as I would > like it to be. According to the man page, it does at least in 6.1-RELEASE. See: http://www.freebsd.org/cgi/man.cgi?query=sh&sektion=1&apropos=0&manpath=FreeBSD+6.1-RELEASE [...] > > 1- If IFS was unset before, it becomes set to the empty string > > after which has a different meaning. > > Your posted script did not unset IFS. Therefore that is not a concern > there. I would not prefer 'command -v' over this because someone > might unset IFS. There are lots of worse things that are possible. I was speaking of the general case: oIFS=$IFS ... IFS=$oIFS doesn't restore IFS in every case. > > 2- word splitting when IFS contains non-blank characters varies > > from one shell to the next, and in most implementations > > (including bash and AT&T ksh, it differs from the way the shell > > splits $PATH internally to look up a command ("/bin:" is "/bin" > > and "" as far as PATH look up is concerned > > Negative. In AT&T ksh (and others) "/bin:" is "/bin" and "." for PATH > lookup. No, it's "/bin" and "". the shell tries to exec "/bin/foo" then "foo", not "/bin/foo" and "./foo". But any what I meant was "/bin:" means /bin and the current directory for PATH lookup, but not for bash word splitting. > > while bash world splitting splits "/bin:" into only "/bin"). > > Negative. In bash "/bin:" is "/bin" and "." for PATH lookup. I was speaking of "bash word splitting" not PATH lookup, that was my whole point: you can't use word splitting that way because it doesn't match the way the shell does the PATH lookup. > > > 3- you forgot to disable filename generation, which means > > wildcards will be expanded in "for p in $PATH" > > Negative. Wildcards will not be expanded there. Yes, they will: Try: foo='a:*:b' IFS=: for i in $foo; do echo "$i"; done regards, Stephane _______________________________________________ Bug-bash mailing list Bug-bash@gnu.org http://lists.gnu.org/mailman/listinfo/bug-bash
