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add pipeline examples (nushell#1748)
* add pipeline examples * Update lang-guide/chapters/pipelines.md Co-authored-by: Darren Schroeder <[email protected]> * Update lang-guide/chapters/pipelines.md Co-authored-by: Darren Schroeder <[email protected]> * Update lang-guide/chapters/pipelines.md Co-authored-by: Darren Schroeder <[email protected]> * update example --------- Co-authored-by: Darren Schroeder <[email protected]>
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‎lang-guide/chapters/pipelines.md‎

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@@ -81,3 +81,161 @@ nu demo.nu o> file.txt o+e>| str upcase
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```
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Also note that `complete` is special, it doesn't work with `e>|`, `o+e>|`.
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## Stdio and redirection behavior examples
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Pipeline and redirection behavior can be hard to follow when they are used with subexpressions, or custom commands. Here are some examples that show intended stdio behavior.
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### Examples for subexpression
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- (^cmd1 | ^cmd2; ^cmd3 | ^cmd4)
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| Command | Stdout | Stderr |
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| ------- | -------- | ---------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | *Terminal* | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | Terminal | Terminal |
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- (^cmd1 | ^cmd2; ^cmd3 | ^cmd4) | ^cmd5
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It runs `(^cmd1 | ^cmd2; ^cmd3 | ^cmd4)` first, then pipes *stdout* to `^cmd5`, where both stdout and stderr are directed to the Terminal.
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| Command | Stdout | Stderr |
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| ------- | -------- | ---------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | *Terminal* | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | Piped | Terminal |
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- (^cmd1 | ^cmd2; ^cmd3 | ^cmd4) e>| ^cmd5
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It runs `(^cmd1 | ^cmd2; ^cmd3 | ^cmd4)` first, then pipes *stderr* to `^cmd5`, where both stdout and stderr are directed to the Terminal.
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | Terminal | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | Terminal | Piped |
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- (^cmd1 | ^cmd2; ^cmd3 | ^cmd4) o+e>| ^cmd5
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It runs `(^cmd1 | ^cmd2; ^cmd3 | ^cmd4)` first, then pipes *stdout and stderr* to `^cmd5`, where both stdout and stderr are directed to the Terminal.
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | Terminal | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | Piped | Piped |
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- (^cmd1 | ^cmd2; ^cmd3 | ^cmd4) o> test.out
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | File | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | File | Terminal |
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- (^cmd1 | ^cmd2; ^cmd3 | ^cmd4) e> test.out
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | File |
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| cmd2 | Terminal | File |
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| cmd3 | Piped | File |
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| cmd4 | Terminal | File |
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- (^cmd1 | ^cmd2; ^cmd3 | ^cmd4) o+e> test.out
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | File |
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| cmd2 | File | File |
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| cmd3 | Piped | File |
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| cmd4 | File | File |
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### Examples for custom command
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Given the following custom commands
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```nushell
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def custom-cmd [] {
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^cmd1 | ^cmd2
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^cmd3 | ^cmd4
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}
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```
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The custom command stdio behavior is the same as the previous section.
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In the examples below the body of `custom-cmd` is `(^cmd1 | ^cmd2; ^cmd3 | ^cmd4)`.
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- custom-cmd
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| Command | Stdout | Stderr |
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| ------- | -------- | ---------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | *Terminal* | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | Terminal | Terminal |
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- custom-cmd | ^cmd5
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It runs `custom-cmd` first, then pipes *stdout* to `^cmd5`, where both stdout and stderr are directed to the Terminal.
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| Command | Stdout | Stderr |
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| ------- | -------- | ---------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | *Terminal* | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | Piped | Terminal |
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- custom-cmd e>| ^cmd5
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It runs `custom-cmd` first, then pipes *stderr* to `^cmd5`, where both stdout and stderr are directed to the Terminal.
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | Terminal | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | Terminal | Piped |
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- custom-cmd o+e>| ^cmd5
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It runs `custom-cmd` first, then pipes *stdout and stderr* to `^cmd5`, where both stdout and stderr are directed to the Terminal.
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | Terminal | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | Piped | Piped |
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- custom-cmd o> test.out
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | Terminal |
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| cmd2 | File | Terminal |
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| cmd3 | Piped | Terminal |
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| cmd4 | File | Terminal |
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- custom-cmd e> test.out
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | File |
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| cmd2 | Terminal | File |
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| cmd3 | Piped | File |
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| cmd4 | Terminal | File |
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- custom-cmd o+e> test.out
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| Command | Stdout | Stderr |
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| ------- | -------- | -------- |
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| cmd1 | Piped | File |
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| cmd2 | File | File |
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| cmd3 | Piped | File |
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| cmd4 | File | File |

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