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mark
2026-01-22 23:08:28 +01:00
commit 974879f55c
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/target

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Cargo.toml Normal file
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[package]
name = "watsch"
version = "1.0.0"
edition = "2024"
[dependencies]
crossterm = "0.29.0"
ctrlc = "3.5.1"

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LICENSE Normal file
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Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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README.md Normal file
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# watsch
`watsch` is a `watch` alternative
```
Usage: watsch [options] [--] <program> <args...>
Options:
-c, --concat
Print program output directly without clearing the screen or resetting the cursor position
-f, --fast, --force
After <program> exits, immediately start it again (same as setting all timing options to zero, currently -i 0 -d 0)
-i, --interval (seconds, default: 1, value: numbers >= 0)
Minimum wait time after <program> is started before starting it again
-d, --delay (seconds, default: 0.1, value: numbers >= 0)
Minimum wait time after <program> exits before starting it again
-x, --fail, --exit
Fail if an error occurs (--fail-exec --fail-with)
--fail-exec
Fail if <program> can't be executed (exit with nonzero exit code instead of retrying)
--fail-with
Fail if <program> fails (exit with <program>'s exit code if it is nonzero)
Notes:
An option's effect may be partially or entirely negated by options specified after it.
This program should prevent flickering by using synchronized updates,
but only some terminals and multiplexers seem to implement this.
```

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src/main.rs Normal file
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use crossterm::{
cursor::{Hide as HideCursor, MoveTo, Show as ShowCursor},
execute,
terminal::{
BeginSynchronizedUpdate, Clear, ClearType, EndSynchronizedUpdate, EnterAlternateScreen,
LeaveAlternateScreen,
},
};
use std::{
ffi::{OsStr, OsString},
process::{Command, ExitCode},
sync::{Arc, Condvar, Mutex},
thread::sleep,
time::{Duration, Instant},
};
fn main() -> ExitCode {
// options
let mut program = None;
let mut interval = Duration::from_secs(1);
let mut delay = Duration::from_secs_f64(0.1);
let mut concat = false;
let mut fail_exec = false;
let mut fail_with = false;
// parse args
let mut exit_code = ExitCode::FAILURE;
let mut args = std::env::args_os().peekable();
let call_name = args.next();
while let Some(arg) = args.next() {
if let Some(arg) = arg.to_str().filter(|&arg| arg.starts_with('-')) {
match arg {
"--" => {
program = args.next();
break;
}
"-h" | "--help" => {
exit_code = ExitCode::SUCCESS;
showhelp(&mut args);
}
"-c" | "--concat" => {
concat = true;
}
"-f" | "--fast" | "--force" => {
interval = Duration::ZERO;
delay = Duration::ZERO;
}
"-i" | "--interval" => {
arg_f64(&mut interval, arg, &mut args);
}
"-d" | "--delay" => {
arg_f64(&mut delay, arg, &mut args);
}
"-x" | "--fail" | "--exit" => {
fail_exec = true;
fail_with = true;
}
"--fail-exec" => {
fail_exec = true;
}
"--fail-with" => {
fail_with = true;
}
_ => {
eprintln!("\nUnknown option {arg}\n");
showhelp(&mut args);
}
}
} else {
program = Some(arg);
break;
}
}
let program = if let Some(p) = program {
p
} else {
eprintln!(
"Usage: {} [options] [--] <program> <args...>{}{}{}{}{}{}{}{}{}{}{}{}",
call_name
.as_ref()
.map_or(OsStr::new("untear"), |n| n)
.display(),
"\nOptions:",
"\n -c, --concat\n Print program output directly without clearing the screen or resetting the cursor position",
"\n -f, --fast, --force\n After <program> exits, immediately start it again (same as setting all timing options to zero, currently -i 0 -d 0)",
"\n -i, --interval (seconds, default: 1, value: numbers >= 0)\n Minimum wait time after <program> is started before starting it again",
"\n -d, --delay (seconds, default: 0.1, value: numbers >= 0)\n Minimum wait time after <program> exits before starting it again",
"\n -x, --fail, --exit\n Fail if an error occurs (--fail-exec --fail-with)",
"\n --fail-exec\n Fail if <program> can't be executed (exit with nonzero exit code instead of retrying)",
"\n --fail-with\n Fail if <program> fails (exit with <program>'s exit code if it is nonzero)",
"\nNotes:",
"\n An option's effect may be partially or entirely negated by options specified after it.",
"\n This program should prevent flickering by using synchronized updates,",
"\n but only some terminals and multiplexers seem to implement this.",
);
return exit_code;
};
exit_code = ExitCode::SUCCESS;
let args = args.collect::<Vec<_>>();
let exit = Arc::new((Mutex::new(false), Condvar::new()));
{
let exit = Arc::clone(&exit);
ctrlc::set_handler(move || {
*exit.0.lock().unwrap() = true;
exit.1.notify_one();
})
.expect("failed to set ctrl-c handler");
}
if !concat {
let _ = execute!(std::io::stdout(), EnterAlternateScreen, HideCursor);
}
let mut next_run = Instant::now();
loop {
if *exit.0.lock().unwrap() {
break;
}
if concat {
let _ = execute!(std::io::stdout(), BeginSynchronizedUpdate);
} else {
let _ = execute!(
std::io::stdout(),
BeginSynchronizedUpdate,
MoveTo(0, 0),
Clear(ClearType::FromCursorDown),
);
}
// spawn command and handle failures
let failure = match Command::new(&program).args(&args).status() {
Ok(s) => {
if s.success() {
false
} else if fail_with {
exit_code = s.code().map_or(ExitCode::FAILURE, |code| {
ExitCode::from((code & 0xFF) as u8)
});
true
} else {
false
}
}
Err(e) => {
eprintln!("{e}");
if fail_exec {
exit_code = ExitCode::FAILURE;
true
} else {
false
}
}
};
let _ = execute!(std::io::stdout(), EndSynchronizedUpdate);
if failure || *exit.0.lock().unwrap() {
break;
}
// wait until start + interval or now + delay, whichever is later,
// but handle ctrl+c using a condvar which the ctrlc handler may notify
let mut now = Instant::now();
next_run = (now + delay).max(next_run + interval);
if loop {
let dur = next_run.saturating_duration_since(now);
// if more than 50ms left, rely on the condvar, else sleep
// normally because the condvar timeout is less accurate
if dur > Duration::from_millis(50) {
match exit.1.wait_timeout_while(
exit.0.lock().unwrap(),
dur - Duration::from_millis(25),
|v| !*v,
) {
Ok((exit, _res)) => {
if *exit {
break true;
}
}
Err(_) => break true,
}
} else {
sleep(dur);
break false;
}
now = Instant::now();
} {
break;
}
}
if !concat {
let _ = execute!(std::io::stdout(), LeaveAlternateScreen, ShowCursor);
}
exit_code
}
// args parsing helper functions
fn showhelp<I: Iterator>(args: &mut I) {
for _ in args {}
}
fn arg_f64<I: Iterator<Item = OsString>>(t: &mut Duration, arg: &str, args: &mut I) {
if let Some(arg) = args.next() {
if let Some(arg) = arg
.to_str()
.and_then(|arg| arg.trim().parse().ok().filter(|v| *v >= 0.0))
{
*t = Duration::from_secs_f64(arg);
} else {
eprintln!("\nExpected a positive number after {}\n", arg.display());
showhelp(args);
}
} else {
eprintln!("\nExpected another argument after {arg}\n");
}
}