idallen@watmath.UUCP (03/24/84)
What does this line in a Bourne Shell command file print, when called
with the command arguments "1 2 3 4"?
sh -c "/bin/echo And $@ were my arguments."
Answer:
And 1
Why? Because of the way "$@" expands, the command line becomes:
sh -c "/bin/echo And 1" "2" "3" "4 were my arguments."
The invoked shell silently ignores the "2" and all following arguments,
and it executes "/bin/echo And 1". I suppose this variation on the
expansion of "$@" makes sense (?!), but what reason is there to silently
ignore the following arguments? (p.s. To fix the problem, change @ to *.)
--
-IAN! (Ian! D. Allen) University of Waterloorpw3@fortune.UUCP (03/25/84)
#R:watmath:-735600:fortune:26900034:000:1844 fortune!rpw3 Mar 24 20:22:00 1984 +-------------------- | sh -c "/bin/echo And 1" "2" "3" "4 were my arguments." | | The invoked shell silently ignores the "2" and all following arguments, | and it executes "/bin/echo And 1". I suppose this variation on the | expansion of "$@" makes sense (?!), but what reason is there to silently | ignore the following arguments? (p.s. To fix the problem, change @ to *.) | -IAN! (Ian! D. Allen) University of Waterloo +-------------------- Sorry, Ian, it isn't "broken". Your "problem" comes from a mis-interpretation of two subtleties: (1) The normal default behaviour of extra arguments, and (2) the meaning of "$@". 1. Any program is allowed to ignore extra arguments, even if some few programs go to great lengths to validate the entire argument string (e.g., "mv"). In this case, "sh -c" is DEFINED to have exactly ONE additional argument to the "-c", which is the command (singular) to be executed. See the man page, which is quite clear about that. It may not be all that polite in your opinion to ignore extra args, but "sh -c cmd" is not usually used by people, but by programs that don't appreciate the extra chatter. (For better or worse, "the UNIX way".) 2. The "$@" construct is doing EXACTLY what it is documented to do. It is NOT a "variation on the expansion", it the ONLY defined meaning. If you want all the positional args collected into ONE "word", use "$*", yes. If you want one "word" for each positional arg, use "$@". It makes a big difference deep down in one's shell scripts which you use. You just used the "wrong" one (that is, if you wanted the other answer). [End of not-a-flame] Rob Warnock UUCP: {sri-unix,amd70,hpda,harpo,ihnp4,allegra}!fortune!rpw3 DDD: (415)595-8444 USPS: Fortune Systems Corp, 101 Twin Dolphin Drive, Redwood City, CA 94065