mirror of
https://github.com/mikefarah/yq.git
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3c0fd6a3e9
Add informational hints to operator documentation covering behaviors
that may differ from user expectations, particularly for those
familiar with jq:
- slice-array: clarify that slicing only works on arrays, not strings
- select: document behavior when piping select to a literal value
- equals: note bash history expansion with != operator
- create-collect-into-object: mention that shorthand {key} syntax
is not supported
- collect-into-array: explain difference between [.x | .[]] and [.x[]]
122 lines
1.9 KiB
Markdown
122 lines
1.9 KiB
Markdown
# Slice/Splice Array
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The slice array operator takes an array as input and returns a subarray. Like the `jq` equivalent, `.[10:15]` will return an array of length 5, starting from index 10 inclusive, up to index 15 exclusive. Negative numbers count backwards from the end of the array.
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You may leave out the first or second number, which will refer to the start or end of the array respectively.
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{% hint style="warning" %}
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_Note_ that slicing only works on arrays, not strings. Using slice syntax on a string (e.g., `.text | .[0:5]`) will return an empty result instead of a substring.
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For string slicing, use split/join or regex:
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```bash
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# Split into array, slice, rejoin
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yq '.text | split("") | .[0:5] | join("")'
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# Or use regex substitution
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yq '.text | sub("^(.{5}).*"; "${1}")'
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```
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{% endhint %}
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## Slicing arrays
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Given a sample.yml file of:
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```yaml
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- cat
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- dog
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- frog
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- cow
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```
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then
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```bash
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yq '.[1:3]' sample.yml
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```
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will output
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```yaml
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- dog
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- frog
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```
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## Slicing arrays - without the first number
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Starts from the start of the array
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Given a sample.yml file of:
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```yaml
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- cat
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- dog
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- frog
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- cow
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```
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then
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```bash
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yq '.[:2]' sample.yml
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```
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will output
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```yaml
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- cat
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- dog
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```
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## Slicing arrays - without the second number
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Finishes at the end of the array
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Given a sample.yml file of:
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```yaml
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- cat
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- dog
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- frog
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- cow
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```
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then
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```bash
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yq '.[2:]' sample.yml
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```
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will output
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```yaml
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- frog
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- cow
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```
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## Slicing arrays - use negative numbers to count backwards from the end
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Given a sample.yml file of:
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```yaml
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- cat
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- dog
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- frog
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- cow
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```
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then
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```bash
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yq '.[1:-1]' sample.yml
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```
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will output
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```yaml
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- dog
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- frog
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```
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## Inserting into the middle of an array
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using an expression to find the index
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Given a sample.yml file of:
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```yaml
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- cat
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- dog
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- frog
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- cow
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```
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then
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```bash
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yq '(.[] | select(. == "dog") | key + 1) as $pos | .[0:($pos)] + ["rabbit"] + .[$pos:]' sample.yml
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```
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will output
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```yaml
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- cat
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- dog
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- rabbit
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- frog
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- cow
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```
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