How to take first n elements in array?

[balki]

Example:

❯ cat ex.yaml                                                   
- foo
- bar
- baz
- blah

Trying to take first 2 elements

❯ yq '.[0:2]' ex.yaml
Error: cannot index array with '' (strconv.ParseInt: parsing "": invalid syntax)

❯ yq '.[0 2]' ex.yaml
Error: Bad expression, please check expression syntax

❯ yq '.[0..2]' ex.yaml
Error: Bad expression, please check expression syntax

This works though but not easy for large n

❯ yq '.[0,1,2]' ex.yaml 
foo
bar
baz

This works but wondering if there is a concise way i am missing.

❯ yq '.[] | select(key < 2)' ex.yaml
foo
bar

[mikefarah]

Hi Balki, adding support for this jq's slice syntax .[0:2] is on the TODO list (#44)

Till then, there isn't a great way to do it - though your trick of .[] | select(key < 2) is quite cool. You may want to wrap it in [] to put it back into an array [.[] | select(key < 2)].

[balki]

Thank you! Is it ok If I try to fix and send a PR?

[mikefarah]

For anything else I'd say go for it, I'm a little hesitant with this as it's fairly deep in yq's hairy core logic - the underlying .[] operator is quite complex, it handles things like .[.name, .cat]?, it'll need to be updated to handle these slices without breaking other random bits...

[mikefarah]

If you're looking for a feature to work on - I'd love help with #1298 - basically yq needs a new merge flag (like these) called t that will make it clobber existing tags (basically disabling the check in UpdateAttributesFrom ``if strings.HasPrefix(n.Node.Tag, "!!") || n.Node.Tag == ""`

It's still reasonably hairy because multiple/merge is the most complex operator...

[balki]

Thank you for the help and suggesting an issue to work on. At the moment, I can't contribute with PR - a bit too complex and not much free time. May be will do in future. Thank you for the amazing tool.