Today I learned that bash has hashmaps (2024)

Post by layer8 » Sat, Jan 11, 2025, 11:21 PM UTC

syntacticbs wrote: post #73

jpavel2 wrote: post #68

Earlier quoted context omitted.

I'm not seeing this local scope leak with bash 5.2.15. The below script works as I'd expect: #!/bin/bash declare -A map1=([x]=2) echo "1. Global scope map1[x]: ${map1[x]}" func1() { echo " * Enter func1" local -A map1 map1[x]=3 echo " Local scope map1[x]: ${map1[x]}" } func1 echo "2. Global scope map1[x]: ${map1[x]}" outputting 1. Global scope map1[x]: 2 * Enter func1 Local scope map1[x]: 3 2. Global scope map1[x]: 2

The local scope leak seems to only happen when you drop down the call stack. See below how I can call func2 from the top level and it's fine, but if I call it from within func1, it will leak. #!/bin/bash declare -A map1=([x]=2) echo "1. Global scope map1[x]: ${map1[x]}" func1() { echo " * Enter func1" local -A map1 map1[x]=3 echo " Local scope map1[x]: ${map1[x]}" func2 } func2() { echo " * Enter func2" echo " Local…

Post by layer8 » Sat, Jan 11, 2025, 11:35 PM UTC

bluedino wrote: post #91

Got burned on this on an interview question before. In a related question I said something about switching to a language like Python when a script started to get "complicated" Then the interviewer explained how his favorite language was bash, how he uses it for everything... I did not get the job. Ironically my next job I did a bunch of Perl to Bash conversion.

Post by layer8 » Sat, Jan 11, 2025, 11:39 PM UTC

dghf wrote: post #19

Picky and probably pointless question: are they actually hashmaps? If I understand correctly, a hashmap isn’t the only way to implement an associative array.

Post by teddyh » Sun, Jan 12, 2025, 1:47 AM UTC

dredmorbius wrote: post #50

teddyh wrote: post #43

Earlier quoted context omitted.

Do you mean PCRE’s “(?&name)” feature? That is not portable; for instance, Python calls it “(?P=name)”. Or do you mean the common feature of “&” in the replacement string meaning “the whole matched string”? While this feature is common in languages which use regexps (including ed, sed, awk, etc.), that’s not actually a regexp feature, since the & character has that effect in the replacement string , not in the regula…

From man(1) less: &pattern Display only lines which match the pattern; lines which do not match the pattern are not displayed. If pattern is empty (if you type & immediately followed by ENTER), any filtering is turned off, and all lines are displayed. While filtering is in effect, an ampersand is displayed at the beginning of the prompt, as a reminder that some lines in the file may be hidden. $ less --version less 4…

Post by fastily » Sun, Jan 12, 2025, 2:01 AM UTC

lars512 wrote: post #56

Unfortunately, MacOS ships an earlier version of bash that does not include associative arrays, so they’re not as portable as you might like.