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std_misc/process/pipe: remove unnecessary enclosing block #704

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Mar 9, 2016
Merged

std_misc/process/pipe: remove unnecessary enclosing block #704

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29 changes: 14 additions & 15 deletions examples/std_misc/process/pipe/pipe.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,23 +15,22 @@ fn main() {
Ok(process) => process,
};

{
// Write a string to the `stdin` of `wc`.
//
// `stdin` has type `Option<ChildStdin>`, but since we know this instance
// must have one, we can directly `unwrap` it.
match process.stdin.unwrap().write_all(PANGRAM.as_bytes()) {
Err(why) => panic!("couldn't write to wc stdin: {}",
Error::description(&why)),
Ok(_) => println!("sent pangram to wc"),
}

// `stdin` gets `drop`ed here, and the pipe is closed.
//
// This is very important, otherwise `wc` wouldn't start processing the
// input we just sent.
// Write a string to the `stdin` of `wc`.
//
// `stdin` has type `Option<ChildStdin>`, but since we know this instance
// must have one, we can directly `unwrap` it.
match process.stdin.unwrap().write_all(PANGRAM.as_bytes()) {
Err(why) => panic!("couldn't write to wc stdin: {}",
Error::description(&why)),
Ok(_) => println!("sent pangram to wc"),
}

// Because `stdin` does not live after the above calls, it is `drop`ed,
// and the pipe is closed.
//
// This is very important, otherwise `wc` wouldn't start processing the
// input we just sent.

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This block (5 lines above this) should probably be removed because it is related to the braces you just removed. It makes little sense without them.

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I left it in (and rephrased it slightly) because it seemed important to mention that the implicit dropping causes ChildStdin to close. (If someone has a let mut stdin = process.stdin;, the program will hang forever.)

Is the phrasing incorrect?

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Ah, I see. If it is important to emphasize that point, you should save it to a variable and include the braces which were just backed out to emphasize the dropping. IDK, I guess it might be nitpicky though. Not sure.

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I don't object to putting the braces back and adding a let mut stdin = to emphasize the dropping, if that's the Rust way of doing things.

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Maybe the wording is just odd. Can't think of anything better right now.

// The `stdout` field also has type `Option<ChildStdout>` so must be unwrapped.
let mut s = String::new();
match process.stdout.unwrap().read_to_string(&mut s) {
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