yq/commands/evaluate.md

description
Evaluates the given expression against each yaml document in each file, in sequence

Evaluate

Note that (as of 4.18.1) this is the default command when none is supplied to yq.

Usage:

yq eval [expression] [yaml_file1]... [flags]

Aliases: eval, e

Note that you can pass in - as a filename to pipe from STDIN.

Examples:

# runs the expression against each file, in series
yq '.a.b | length' f1.yml f2.yml 

# '-' will pipe from STDIN
cat file.yml | yq '.a.b' f1.yml -  f2.yml

# prints out the file
yq sample.yaml 
cat sample.yml | yq e

# prints a new yaml document
yq -n '.a.b.c = "cat"' 

# updates file.yaml directly
yq '.a.b = "cool"' -i file.yaml 

Flags:

  -h, --help          help for eval
  -C, --colors        force print with colors
  -e, --exit-status   set exit status if there are no matches or null or false is returned
  -I, --indent int    sets indent level for output (default 2)
  -i, --inplace       update the yaml file inplace of first yaml file given.
  -M, --no-colors     force print with no colors
  -N, --no-doc        Don't print document separators (---)
  -n, --null-input    Don't read input, simply evaluate the expression given. Useful for creating yaml docs from scratch.
  -j, --tojson        output as json. Set indent to 0 to print json in one line.
  -v, --verbose       verbose mode