watch: add initial version

Cargo.lock

@@ -442,6 +442,7 @@ dependencies = [
  "uu_free",
  "uu_pwdx",
  "uu_w",
+ "uu_watch",
  "uucore",
  "xattr",
 ]
@@ -794,6 +795,14 @@ dependencies = [
  "uucore",
 ]
 
+[[package]]
+name = "uu_watch"
+version = "0.0.1"
+dependencies = [
+ "clap",
+ "uucore",
+]
+
 [[package]]
 name = "uucore"
 version = "0.0.24"

Cargo.toml

@@ -28,6 +28,7 @@ feat_common_core = [
   "pwdx",
   "free",
   "w",
+  "watch",
 ]
 
 [workspace.dependencies]
@@ -59,6 +60,7 @@ textwrap = { workspace = true }
 pwdx = { optional = true, version = "0.0.1", package = "uu_pwdx", path = "src/uu/pwdx" }
 free = { optional = true, version = "0.0.1", package = "uu_free", path = "src/uu/free" }
 w = { optional = true, version = "0.0.1", package = "uu_w", path = "src/uu/w" }
+watch = { optional = true, version = "0.0.1", package = "uu_watch", path = "src/uu/watch" }
 
 [dev-dependencies]
 pretty_assertions = "1"

src/uu/watch/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "uu_watch"
+version = "0.0.1"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+uucore = { workspace = true }
+clap = { workspace = true }
+
+[lib]
+path = "src/watch.rs"
+
+[[bin]]
+name = "watch"
+path = "src/main.rs"

src/uu/watch/src/watch.rs

@@ -0,0 +1,61 @@
+// This file is part of the uutils procps package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use clap::{Arg, ArgAction, Command};
+use clap::{crate_version};
+use std::process::{Command as SystemCommand, Stdio};
+use std::thread::sleep;
+use std::time::Duration;
+use uucore::{error::UResult, format_usage, help_about, help_usage};
+
+const ABOUT: &str = help_about!("watch.md");
+const USAGE: &str = help_usage!("watch.md");
+
+#[uucore::main]
+pub fn uumain(args: impl uucore::Args) -> UResult<()> {
+    let matches = uu_app().try_get_matches_from(args)?;
+
+    let command_to_watch = matches.get_one::<String>("command").expect("required argument");
+    let interval = 2; // TODO matches.get_one::<u64>("interval").map_or(2, |&v| v);
+
+    loop {
+        let output = SystemCommand::new("sh")
+            .arg("-c")
+            .arg(command_to_watch)
+            .stdout(Stdio::inherit())
+            .stderr(Stdio::inherit())
+            .output()?;
+
+        if !output.status.success() {
+            eprintln!("watch: command failed: {:?}", output.status);
+            break;
+        }
+
+        sleep(Duration::from_secs(interval));
+    }
+
+    Ok(())
+}
+
+pub fn uu_app() -> Command {
+    Command::new(uucore::util_name())
+        .version(crate_version!())
+        .about(ABOUT)
+        .override_usage(format_usage(USAGE))
+        .infer_long_args(true)
+        .arg(
+            Arg::new("command")
+                .required(true)
+                .help("Command to be executed"),
+        )
+        .arg(
+            Arg::new("interval")
+                .short('n')
+                .long("interval")
+                .default_value("2")
+                .help("Seconds to wait between updates")
+                .action(ArgAction::Set),
+        )
+}

src/uu/watch/watch.md

@@ -0,0 +1,7 @@
+# watch
+
+```
+watch [options] command
+```
+
+Execute a program periodically, showing output fullscreen

tests/by-util/test_watch.rs

@@ -0,0 +1,14 @@
+// This file is part of the uutils procps package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+// spell-checker:ignore (words) symdir somefakedir
+
+use std::path::PathBuf;
+
+use crate::common::util::{TestScenario, UCommand};
+
+#[test]
+fn test_invalid_arg() {
+    new_ucmd!().arg("--definitely-invalid").fails().code_is(1);
+}

tests/tests.rs

@@ -16,3 +16,7 @@ mod test_free;
 #[cfg(feature = "w")]
 #[path = "by-util/test_w.rs"]
 mod test_w;
+
+#[cfg(feature = "watch")]
+#[path = "by-util/test_watch.rs"]
+mod test_watch;