dash/ash [LWN.net]

dash/ash

Posted Oct 2, 2014 14:23 UTC (Thu) by nix (subscriber, #2304)
In reply to: dash/ash by Jandar
Parent article: Bash gets shellshocked

There are things you can do with arrays stored as files that you can't do in any other way -- e.g. high-speed filtration and set-membership queries with comm(1) and grep. Since the primary priority when making a shell script fast enough to be useful is converting all loops into pipelines, and comm(1) is invaluable in that, I'm not sure why you'd ever want to use arrays in any other form, really.

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dash/ash

Posted Oct 3, 2014 9:48 UTC (Fri) by Jandar (subscriber, #85683) [Link] (2 responses)

With arrays the construction of an argument-vector is easy.

typeset -a Options Files
Options+=("$option1")
Files+=("$file1")
$UseVerbose && Options+=("-v")
$UseSecondFile && Files+=("$file2")
command "${Options[@]}" -- "${Files[@]}"

How do you prepare (with correct quoting) a dynamic argument-vector without arrays? All other methods are ugly and error-prone beyond any acceptable limit.

dash/ash

Posted Oct 17, 2014 11:12 UTC (Fri) by mgedmin (guest, #34497) [Link] (1 responses)

Thank you. I've been reading bash(1) and tearing my hair out, and the only syntax I discovered for appending an item to an array was

paths[${#paths[*]}]="$1"

Rewriting this to use +=() will make my scripts a bit saner.

dash/ash

Posted Oct 17, 2014 12:02 UTC (Fri) by mathstuf (subscriber, #69389) [Link]

Any reason path=( "$path[@]" "$1" ) wouldn't have worked?