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Make stderr logging handle CR-separated progress output #79

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Merged
merged 1 commit into from
Aug 1, 2025
Merged

Make stderr logging handle CR-separated progress output #79

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8 changes: 8 additions & 0 deletions examples/progress.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
use cmd_lib::{run_cmd, CmdResult};

#[cmd_lib::main]
fn main() -> CmdResult {
run_cmd!(dd if=/dev/urandom of=/dev/null bs=1M status=progress)?;

Ok(())
}
76 changes: 63 additions & 13 deletions src/child.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -342,22 +342,72 @@ struct StderrThread {
impl StderrThread {
fn new(cmd: &str, file: &str, line: u32, stderr: Option<PipeReader>, capture: bool) -> Self {
if let Some(stderr) = stderr {
let file_ = file.to_owned();
let thread = std::thread::spawn(move || {
let mut output = String::new();
BufReader::new(stderr)
.lines()
.map_while(Result::ok)
.for_each(|line| {
if !capture {
info!("{line}");
} else {
if !output.is_empty() {
output.push('\n');
if capture {
let mut output = String::new();
BufReader::new(stderr)
.lines()
.map_while(Result::ok)
.for_each(|line| {
if !capture {
info!("{line}");
} else {
if !output.is_empty() {
output.push('\n');
}
output.push_str(&line);
}
output.push_str(&line);
});
return output;
}

// Log output one line at a time, including progress output separated by CR
let mut reader = BufReader::new(stderr);
let mut buffer = vec![];
loop {
// Unconditionally try to read more data, since the BufReader buffer is empty
let result = match reader.fill_buf() {
Ok(buffer) => buffer,
Err(error) => {
warn!("Error reading from child process: {error:?} at {file_}:{line}");
break;
}
};
// Add the result onto our own buffer
buffer.extend(result);
// Empty the BufReader
let read_len = result.len();
reader.consume(read_len);

// Log output. Take whole “lines” at every LF or CR (for progress bars etc),
// but leave any incomplete lines in our buffer so we can try to complete them.
while let Some(offset) = buffer.iter().position(|&b| b == b'\n' || b == b'\r') {
let line = &buffer[..offset];
let line = str::from_utf8(line).map_err(|_| line);
match line {
Ok(string) => info!("{string}"),
Err(bytes) => info!("{bytes:?}"),
}
});
output
buffer = buffer.split_off(offset + 1);
}

if read_len == 0 {
break;
}
}

// Log any remaining incomplete line
if !buffer.is_empty() {
let line = &buffer;
let line = str::from_utf8(line).map_err(|_| line);
match line {
Ok(string) => info!("{string}"),
Err(bytes) => info!("{bytes:?}"),
}
}

"".to_owned()
});
Self {
cmd: cmd.into(),
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