Subtract

You can use subtract to subtract numbers as well as remove elements from an array.

Array subtraction

Running

bash

yq --null-input '[1,2] - [2,3]'

will output

yaml

- 1

Array subtraction with nested array

Running

bash

yq --null-input '[[1], 1, 2] - [[1], 3]'

will output

yaml

- 1
- 2

Array subtraction with nested object

Note that order of the keys does not matter

Given a sample.yml file of:

yaml

- a: b
  c: d
- a: b

then

bash

yq '. - [{"c": "d", "a": "b"}]' sample.yml

will output

yaml

- a: b

Number subtraction - float

If the lhs or rhs are floats then the expression will be calculated with floats.

Given a sample.yml file of:

yaml

a: 3
b: 4.5

then

bash

yq '.a = .a - .b' sample.yml

will output

yaml

a: -1.5
b: 4.5

Number subtraction - int

If both the lhs and rhs are ints then the expression will be calculated with ints.

Given a sample.yml file of:

yaml

a: 3
b: 4

then

bash

yq '.a = .a - .b' sample.yml

will output

yaml

a: -1
b: 4

Decrement numbers

Given a sample.yml file of:

yaml

a: 3
b: 5

then

bash

yq '.[] -= 1' sample.yml

will output

yaml

a: 2
b: 4

Date subtraction

You can subtract durations from dates. Assumes RFC3339 date time format, see date-time operators for more information.

Given a sample.yml file of:

yaml

a: 2021-01-01T03:10:00Z

then

bash

yq '.a -= "3h10m"' sample.yml

will output

yaml

a: 2021-01-01T00:00:00Z

Date subtraction - custom format

Use with_dtf to specify your datetime format. See date-time operators for more information.

Given a sample.yml file of:

yaml

a: Saturday, 15-Dec-01 at 6:00AM GMT

then

bash

yq 'with_dtf("Monday, 02-Jan-06 at 3:04PM MST", .a -= "3h1m")' sample.yml

will output

yaml

a: Saturday, 15-Dec-01 at 2:59AM GMT

Custom types: that are really numbers

When custom tags are encountered, yq will try to decode the underlying type.

Given a sample.yml file of:

yaml

a: !horse 2
b: !goat 1

then

bash

yq '.a -= .b' sample.yml

will output

yaml

a: !horse 1
b: !goat 1