String Operators

String Operators
RegEx
This uses golangs native regex functions under the hood - See https://github.com/google/re2/wiki/Syntax for the supported syntax.
String blocks, bash and newlines
Bash is notorious for chomping on precious trailing newline characters, making it tricky to set strings with newlines properly. In particular, the $( exp ) will trim trailing newlines.
For instance to get this yaml:
a: |
  cat
Using $( exp ) wont work, as it will trim the trailing new line.
m=$(echo "cat\n") yq e -n '.a = strenv(m)'
a: cat
However, using printf works:
printf -v m "cat\n" ; m="$m" yq e -n '.a = strenv(m)'
a: |
  cat
As well as having multiline expressions:
m="cat
"  yq e -n '.a = strenv(m)'
a: |
  cat
Similarly, if you're trying to set the content from a file, and want a trailing new line:
IFS= read -rd '' output < <(cat my_file)
output=$output ./yq e '.data.values = strenv(output)' first.yml
Join strings
Given a sample.yml file of:
- cat
- meow
- 1
- null
- true
then
yq eval 'join("; ")' sample.yml
will output
cat; meow; 1; ; true
Match string
Given a sample.yml file of:
foo bar foo
then
yq eval 'match("foo")' sample.yml
will output
string: foo
offset: 0
length: 3
captures: []
Match string, case insensitive
Given a sample.yml file of:
foo bar FOO
then
yq eval '[match("(?i)foo"; "g")]' sample.yml
will output
- string: foo
  offset: 0
  length: 3
  captures: []
- string: FOO
  offset: 8
  length: 3
  captures: []
Match with capture groups
Given a sample.yml file of:
abc abc
then
yq eval '[match("(abc)+"; "g")]' sample.yml
will output
- string: abc
  offset: 0
  length: 3
  captures:
    - string: abc
      offset: 0
      length: 3
- string: abc
  offset: 4
  length: 3
  captures:
    - string: abc
      offset: 4
      length: 3
Match with named capture groups
Given a sample.yml file of:
foo bar foo foo  foo
then
yq eval '[match("foo (?P<bar123>bar)? foo"; "g")]' sample.yml
will output
- string: foo bar foo
  offset: 0
  length: 11
  captures:
    - string: bar
      offset: 4
      length: 3
      name: bar123
- string: foo  foo
  offset: 12
  length: 8
  captures:
    - string: null
      offset: -1
      length: 0
      name: bar123
Capture named groups into a map
Given a sample.yml file of:
xyzzy-14
then
yq eval 'capture("(?P<a>[a-z]+)-(?P<n>[0-9]+)")' sample.yml
will output
a: xyzzy
n: "14"
Match without global flag
Given a sample.yml file of:
cat cat
then
yq eval 'match("cat")' sample.yml
will output
string: cat
offset: 0
length: 3
captures: []
Match with global flag
Given a sample.yml file of:
cat cat
then
yq eval '[match("cat"; "g")]' sample.yml
will output
- string: cat
  offset: 0
  length: 3
  captures: []
- string: cat
  offset: 4
  length: 3
  captures: []
Test using regex
Like jq'q equivalant, this works like match but only returns true/false instead of full match details
Given a sample.yml file of:
- cat
- dog
then
yq eval '.[] | test("at")' sample.yml
will output
true
false
Substitute / Replace string
This uses golang regex, described here Note the use of |= to run in context of the current string value.
Given a sample.yml file of:
a: dogs are great
then
yq eval '.a |= sub("dogs", "cats")' sample.yml
will output
a: cats are great
Substitute / Replace string with regex
This uses golang regex, described here Note the use of |= to run in context of the current string value.
Given a sample.yml file of:
a: cat
b: heat
then
yq eval '.[] |= sub("(a)", "${1}r")' sample.yml
will output
a: cart
b: heart
Split strings
Given a sample.yml file of:
cat; meow; 1; ; true
then
yq eval 'split("; ")' sample.yml
will output
- cat
- meow
- "1"
- ""
- "true"
Split strings one match
Given a sample.yml file of:
word
then
yq eval 'split("; ")' sample.yml
will output
- word
Split into Documents
Style
Last updated 1 week ago