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

There was a bug in the One True Shell (/bin/sh on V7) such that a simple "$@" would fail miserably if nothing at all was passed. So we old-timers learned to write the extended version instead. Since the code that generates that #! line was no doubt written in the Perl1 days, the legacy was carried forward, although no modern shell probably still suffers the same bug.

-- Randal L. Schwartz, Perl hacker

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

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Re^2: what's the difference between "$@" and ${1+"$@"} (misery) by tye (Sage) on Oct 06, 2007 at 01:49 UTC
such that a simple "$@" would fail miserably if nothing at all was passed "fail miserably" meant (on my systems back then, anyway) that `""` (a single empty argument) got passed instead of no arguments. It was considered more of a design quirk than a bug in my neighborhood, since it made sense for `$@` to expand to something like `foo" "bar` (if two arguments were passed) but didn't make as much sense for `$@` to make surrounding quotes, if present, just magically disappear (if no arguments passed). - tye	[reply] [d/l] [select]
Re^2: what's the difference between "$@" and ${1+"$@"} by cadphile (Beadle) on Oct 09, 2007 at 16:56 UTC
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 `$1`, which happens also to be empty? Or does the `1+` just act to clean up the return value of the empty `"$@"`.	[reply] [d/l] [select]
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]