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A *complete* listing of operators in Nix, and their predence.

This article was originally published at https://gist.github.com/joepie91/c3c047f3406aea9ec65eebce2ffd449d.

The information in this article has since been absorbed into the official Nix manual. It is kept here for posterity. It may be outdated by the time you read this.

Lower precedence means a stronger binding; ie. this list is sorted from strongest to weakest binding, and in the case of equal precedence between two operators, the associativity decides the binding.

Prec Abbreviation Example Assoc Description
1 SELECT e . attrpath [or def] none Select attribute denoted by the attribute path attrpath from set e. (An attribute path is a dot-separated list of attribute names.) If the attribute doesn’t exist, return default if provided, otherwise abort evaluation.
2 APP e1 e2 left Call function e1 with argument e2.
3 NEG -e none Numeric negation.
4 HAS_ATTR e ? attrpath none Test whether set e contains the attribute denoted by attrpath; return true or false.
5 CONCAT e1 ++ e2 right List concatenation.
6 MUL e1 * e2 left Numeric multiplication.
6 DIV e1 / e2 left Numeric division.
7 ADD e1 + e2 left Numeric addition, or string concatenation.
7 SUB e1 - e2 left Numeric subtraction.
8 NOT !e left Boolean negation.
9 UPDATE e1 // e2 right Return a set consisting of the attributes in e1 and e2 (with the latter taking precedence over the former in case of equally named attributes).
10 LT e1 < e2 left Less than.
10 LTE e1 <= e2 left Less than or equal.
10 GT e1 > e2 left Greater than.
10 GTE e1 >= e2 left Greater than or equal.
11 EQ e1 == e2 none Equality.
11 NEQ e1 != e2 none Inequality.
12 AND e1 && e2 left Logical AND.
13 OR e1 || e2 left Logical OR.
14 IMPL e1 -> e2 none Logical implication (equivalent to !e1 || e2).
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