On 7/3/20 2:00 PM, Chris Elvidge wrote: > I've used 'return $((!$#))' and 'return $[!$#]' to return an error if no > parameters given to function. > > Tested in a bash script 'exit $((!$#)) / $[!$#]' - both work. > > 'echo $((!$#)) / $[!$#]' - both echo 1 when no params, 0 when any > number of params. > > I'm told ( https://wiki.bash-hackers.org/scripting/obsolete ) that > $[...] is obsolete and that $((...)) should be used instead. OK so far. > > However 'N=0; echo $((!$N))' gives an error at the bash prompt. 'echo > $[!$N]' echo's 1 as expected.
"gives an error" is a useless bug report. It works for me. $ N=0; echo $((!$N)) 1 My initial reaction to reading this thread is head scratching! As the other reply mentioned, there's actually a good explanation for why we get different results -- I disabled an annoying feature. $ set -o histexpand Now here's a useful bug report. "When I run this, I get the following incorrect results or error message": $ N=0; echo $((!$N)) N=0; echo $((histexpandN)) 0 $ N=0; echo $((!$N)) N=0; echo $(()N)) -bash: syntax error near unexpected token `)' $ N=0 $ echo $((!$N)) echo $((N=0N)) -bash: N=0N: value too great for base (error token is "0N") ... From there, people can give useful advice for solving the problem. (My preferred advice is "disable histexpand".) -- Eli Schwartz Arch Linux Bug Wrangler and Trusted User
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