On Fri, Jun 13, 2025 at 07:08:21 -0600, Stan Marsh wrote: > BTW, and only tangentially related, "man bash" says that "let" and "(( ))" > are exactly > the same, but "shellcheck" thinks otherwise. "shellcheck" says you should > use "(( ))" > and never use "let", but I still (mostly) use "let".
That's peculiar. I'm not sure why shellcheck would advise using one of them over the other, and in particular, why it would advise (( over let. Maybe it's because of quoting issues with let? It's been my experience that (( looks nicer (because of the aforementioned quoting issues), but let is *safer* in at least one case. According to <https://mywiki.wooledge.org/BashPitfalls#pf62>: (( hash[$key]++ )) # is not safe let 'hash[$key]++' # is safe It seems to be version-dependent, which the wiki page is not clear about. (starting in bash-5.2) hobbit:~$ unset hash hobbit:~$ declare -A hash; key=\'\] hobbit:~$ (( hash[$key]++ )) hobbit:~$ declare -p hash declare -A hash=(["']"]="1" ) hobbit:~$ bash-5.1 hobbit:~$ declare -A hash; key=\'\] hobbit:~$ (( hash[$key]++ )) bash-5.1: ((: hash[']]++ : bad array subscript (error token is "hash[']]++ ") hobbit:~$ let 'hash[$key]++' hobbit:~$ declare -p hash declare -A hash=(["']"]="1" ) So, at least if the goal is to write code that works in multiple versions of bash, let is definitely safer than (( in this case.
