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Dec 22, 2022
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Add section "Output result to external commands" #713

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Add section "Output result to external commands"
Tengs-Fan Dec 22, 2022
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Update pipelines.md
Tengs-Fan Dec 22, 2022
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Update book/pipelines.md
Tengs-Fan Dec 22, 2022
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Update book/pipelines.md
Tengs-Fan Dec 22, 2022
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44 changes: 44 additions & 0 deletions book/pipelines.md
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Expand Up @@ -83,3 +83,47 @@ And the pipeline:
```

Are one and the same.

## Output result to external commands

Sometimes you want to output Nushell structured data to an external command for further processing. However, Nushell's default formatting options for structured data may not be what you want.
For example, you want to find a file named "tutor" under "/usr/share/vim/runtime" and check its ownership

```
> ls /usr/share/nvim/runtime/
╭────┬───────────────────────────────────────┬──────┬─────────┬───────────────╮
│ # │ name │ type │ size │ modified │
├────┼───────────────────────────────────────┼──────┼─────────┼───────────────┤
│ 0 │ /usr/share/nvim/runtime/autoload │ dir │ 4.1 KB │ 2 days ago │
..........
..........
..........

│ 31 │ /usr/share/nvim/runtime/tools │ dir │ 4.1 KB │ 2 days ago │
│ 32 │ /usr/share/nvim/runtime/tutor │ dir │ 4.1 KB │ 2 days ago │
├────┼───────────────────────────────────────┼──────┼─────────┼───────────────┤
│ # │ name │ type │ size │ modified │
╰────┴───────────────────────────────────────┴──────┴─────────┴───────────────╯
```

You decided to use `grep` and [pipe](https://www.nushell.sh/book/pipelines.html) the result to external `^ls`

```
> ls /usr/share/nvim/runtime/ | get name | ^grep tutor | ^ls -la $in
ls: cannot access ''$'\342\224\202'' 32 '$'\342\224\202'' /usr/share/nvim/runtime/tutor '$'\342\224\202\n': No such file or directory
```

What's wrong? Nushell renders lists and tables (by adding a border with characters like `╭`,`─`,`┬`,`╮`) before piping them as text to external commands. If that's not the behavior you want, you must explicitly convert the data to a string before piping it to an external. For example, you can do so with [`to text`](commands/to_text.md):

```
> ls /usr/share/nvim/runtime/ | get name | to text | ^grep tutor | tr -d '\n' | ^ls -la $in
total 24
drwxr-xr-x@ 5 pengs admin 160 14 Nov 13:12 .
drwxr-xr-x@ 4 pengs admin 128 14 Nov 13:42 en
-rw-r--r--@ 1 pengs admin 5514 14 Nov 13:42 tutor.tutor
-rw-r--r--@ 1 pengs admin 1191 14 Nov 13:42 tutor.tutor.json
```
(Actually, for this simple usage you can just use [`find`](commands/find.md))
```
> ls /usr/share/nvim/runtime/ | get name | find tutor | ^ls -al $in
```