Add "Process child process output continuously" example #373
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budziq
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budziq
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Thanks @ludwigpacifici !
Some suggestions below
src/basics.md
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| println!("{}", line); | ||
| } | ||
| } | ||
| # |
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the Ok(()) might be a boilerplate but lets not hide it as it is necessary to compile the example when copy pasted
src/basics.md
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| | [Run an external command passing it stdin and check for an error code][ex-parse-subprocess-input] | [![regex-badge]][regex] | [![cat-os-badge]][cat-os] [![cat-text-processing-badge]][cat-text-processing] | | ||
| | [Run piped external commands][ex-run-piped-external-commands] | [![std-badge]][std] | [![cat-os-badge]][cat-os] | | ||
| | [Redirect both stdout and stderr of child process to the same file][ex-redirect-stdout-stderr-same-file] | [![std-badge]][std] | [![cat-os-badge]][cat-os] | | ||
| | [Continuously process child process' outputs][ex-continuous-process-output] | [![std-badge]][std] | [![cat-os-badge]][cat-os] | |
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hmm text-processing badge might make sense. What are your thoughts @ludwigpacifici ?
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Yep. Plus it will be homogeneous with similar recipes like Run an external command and process stdout.
src/basics.md
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| let reader = BufReader::new(stdout); | ||
| for line in reader.lines() { |
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how about we try to express this in a functional style with filter_map filter and for_each?
src/basics.md
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| # extern crate error_chain; | ||
| # | ||
| use std::process::{Command, Stdio}; | ||
| use std::io::BufReader; |
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hmm, I remember rustfmt was doing this for me before. But not now. Anyway, let's group them.
src/basics.md
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| stdout](#ex-parse-subprocess-output), while an external [`Command`] is | ||
| running, process its standard output. A new pipe is created by | ||
| [`Stdio::piped`] and it is read by a [`BufReader`]. Note, a buffered | ||
| reader uses a buffer to reduce the number of I/O requests. |
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I'm not sure that we need to explain what BufReader does
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True, it's slightly off topic. While I was implementing the example, I ask myself the question std::io::BufReader vs std::io::Reader. I will remove it. Plus the BufReader link to the doc explains it:
It can be excessively inefficient to work directly with a Read instance. For example, every call to read on TcpStream results in a system call. A BufReader performs large, infrequent reads on the underlying Read and maintains an in-memory buffer of the results.
src/basics.md
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| Contrary to [Run an external command and process | ||
| stdout](#ex-parse-subprocess-output), while an external [`Command`] is | ||
| running, process its standard output. A new pipe is created by |
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the explanation is slightly unclear. I'd emphasize that the we do not wait for the child process to finish and process the output continuously.
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fixes #339
Hello @budziq ! Another PR :-) I also added a commit to update the std badge version.