BASH - Variable name from variable

Question

my code

TOTAL=${#FOO_5[*]} // COUNT ITEMS IN ARRAY

what if code

ARRAY_NAME="FOO_5"
TOTAL=${#${!ARRAY_NAME}[*]} //error

please fix

Don't guess randomly at shell syntax.

ormaaj
– ormaaj

2012-10-14 12:21:45 +00:00
Commented Oct 14, 2012 at 12:21 — ormaaj
– ormaaj, Commented Oct 14, 2012 at 12:21

chepner · Accepted Answer · 2012-10-14 12:52:21Z

2

When it comes to indirect parameter expansion, the array index is considered part of the parameter name. Unfortunately, you cannot chain parameter expansions; you'll also need a intermediate variable.

ARRAY_NAME="FOO_5[*]"
FULL=${!ARRAY_NAME}
TOTAL=${#FULL}

answered Oct 14, 2012 at 12:52

chepner

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3 Comments

ormaaj Over a year ago

ugh. recommend associative arrays before this hack. Especially to "all-caps variable users".

ormaaj Over a year ago

Also forgot to mention, remember "${#a[*]}" and "${#a[@]}" are equivalent, so this is probably not what he wants. full=("${!arr}") total=${#full[@]}. I'd just eval.

chepner Over a year ago

Right, I missed the comment that said "count items in array".

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