# How do I know if an unbuffered (0 sized) channel ready to put! (not blocking)?

**URL:** https://discourse.julialang.org/t/how-do-i-know-if-an-unbuffered-0-sized-channel-ready-to-put-not-blocking/65228
**Category:** General Usage
**Tags:** question, channel
**Created:** [July 24, 2021, 10:43am UTC](https://discourse.julialang.org/t/how-do-i-know-if-an-unbuffered-0-sized-channel-ready-to-put-not-blocking/65228 "2021-07-24T10:43:47Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![zwtechnb](https://avatars.discourse-cdn.com/v4/letter/z/65b543/32.png) [@zwtechnb](https://discourse.julialang.org/u/zwtechnb)
#### Post date: [July 24, 2021, 10:43am UTC](https://discourse.julialang.org/t/how-do-i-know-if-an-unbuffered-0-sized-channel-ready-to-put-not-blocking/65228/1 "2021-07-24T10:43:48Z")

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For a buffered channel(n) with n\>0, I can check it full or not with comparing the Channel field: `sz_max` with the undocumented function `Base.n_avail(channel)`.

For channel(0), when a `take!` on it, a `put!` can be operated on this 0-sized channel without blocking. How do I know if channel(0) is NOT blocking to `put!` ?

Much THX