Re^2: what's the difference between "$@" and ${1+"$@"}

The syntax isn't quite ${1:+$foo}, and hence "this" or "that". I've never seen any documentation of the syntax ${foo+"$bar"}.

I'm just curious what the 1+ does in this context. If there are actual arguments in "$@", the 1+ doesn't seem to modify the end result at all. So, if "$@" is empty, do we get instead the return value of the first positional parameter $1, which happens also to be empty? Or does the 1+ just act to clean up the return value of the empty "$@".

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Re^3: what's the difference between "$@" and ${1+"$@"} by ikegami (Patriarch) on Oct 09, 2007 at 17:05 UTC
From the manual, If the colon (:) is omitted from the above expressions, the shell only checks whether parameter is set or not.	[reply]
Re^4: what's the difference between "$@" and ${1+"$@"} by cadphile (Beadle) on Oct 11, 2007 at 22:39 UTC
Aha! Now it makes sense. Thanks everyone, especially Merlin, for your imparted wisdom... And I finally found a web page that discusses this, with some good background detail. http://www.in-ulm.de/~mascheck/various/bourne_args As an interesting side note, I wonder if anyone knows how to give this string (`${1+"$@"}`) to Google's search engine. As is, it doesn't work. I tried single-quoting it, and it still doesn't work. Cadphile...	[reply] [d/l]