Multi tool use

Clash Royale CLAN TAG

Do jq's variable bindings work through functions?

I have the following script for jq:

$ jq -n 'def f: $a; 1 as $a | $a'
1


Since f is not used, this outputs 1 as expected. However:

f

1

$ jq -n 'def f: $a; 1 as $a | f'
jq: error: a/0 is not defined at <top-level>, line 1:
def f: $a; 1 as $a | f
jq: 1 compile error


Is it not possible to use variable bindings through functions?

1 Answer
1

In jq, the scoping of variables is defined lexically. With f defined as $a, f can only be evaluated as $a if $a is "visible" to f. This can be achieved, for example, using one of the command-line options such as —arg or —argjson.

f

$a

f

$a

$a

f

It can also be achieved as illustrated by:

jq -n '2 as $a | def f: $a; f'


Note also that lexical scoping works with sub-functions as well:

def f($a): def g: $a; g;
f(1)


yields:

1


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