Struct Capture 

pub struct Capture { /* private fields */ }

Two anonymous files that collect a child’s standard output and standard error.

Implementations

impl Capture

pub fn new() -> Result<Self>

Two new empty anonymous files.

pub fn stdio(&self) -> Result<(Stdio, Stdio)>

The two files as the standard output and standard error of a child.

pub fn snapshot(&self, limit: usize) -> Captured

What: A snapshot of what the child wrote so far to each stream: the last limit bytes of what was there when the snapshot began, and a note for everything that was left out. Why: A descendant that keeps appending, or a child that writes more than anyone wants, must not make the reader chase the end of a file that grows ahead of it, nor hold the whole of it in memory (sol-1 and sol-2 round 2): the length is read once and that many bytes are read at most, from the end of the snapshot backwards by limit. A read that fails is not the end of the output: the stream’s note says it could not be read whole. The tail is kept because a tool prints its reason last.

In TS you’d write (pseudocode):

const { stdout, stderr, notes } = capture.snapshot(limit);

pub fn discard(&self)

Free what the files hold in memory. The child’s offset is its own, so what it writes afterwards leaves a hole before it and costs only the pages it writes; nothing reads the files after this.