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# Description
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This is inspired by the Unix tee command, but significantly more
powerful. Rather than just writing to a file, you can do any kind of
stream operation that Nushell supports within the closure.
The equivalent of Unix `tee -a file.txt` would be, for example, `command
| tee { save -a file.txt }` - but of course this is Nushell, and you can
do the same with structured data to JSON objects, or even just run any
other command on the system with it.
A `--stderr` flag is provided for operating on the stderr stream from
external programs. This may produce unexpected results if the stderr
stream is not then also printed by something else - nushell currently
doesn't. See #11929 for the fix for that.
# User-Facing Changes
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If someone was using the system `tee` command, they might be surprised
to find that it's different.
# Tests + Formatting
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sure to [enable developer
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- `cargo run -- -c "use std testing; testing run-tests --path
crates/nu-std"` to run the tests for the standard library
> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```
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- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`
# After Submitting
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