From 1f24b1f59c90bda4eabef404dcebaad81b590c5a Mon Sep 17 00:00:00 2001
From: Jan Scheer <jhscheer@users.noreply.github.com>
Date: Thu, 16 Sep 2021 17:14:23 +0200
Subject: [PATCH] tail: implement sub-second sleep interval e.g. `-s.1`

---
 src/uu/tail/src/tail.rs    | 18 +++++++++---------
 tests/by-util/test_tail.rs | 10 ++++++++++
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/src/uu/tail/src/tail.rs b/src/uu/tail/src/tail.rs
index 89fbe4d36..7ba741c5e 100644
--- a/src/uu/tail/src/tail.rs
+++ b/src/uu/tail/src/tail.rs
@@ -27,6 +27,7 @@ use std::io::{stdin, stdout, BufRead, BufReader, Read, Seek, SeekFrom, Write};
 use std::path::Path;
 use std::thread::sleep;
 use std::time::Duration;
+use uucore::display::Quotable;
 use uucore::parse_size::{parse_size, ParseSizeError};
 use uucore::ringbuffer::RingBuffer;
 
@@ -56,7 +57,7 @@ enum FilterMode {
 
 struct Settings {
     mode: FilterMode,
-    sleep_msec: u32,
+    sleep_sec: Duration,
     beginning: bool,
     follow: bool,
     pid: platform::Pid,
@@ -66,7 +67,7 @@ impl Default for Settings {
     fn default() -> Settings {
         Settings {
             mode: FilterMode::Lines(10, b'\n'),
-            sleep_msec: 1000,
+            sleep_sec: Duration::from_secs_f32(1.0),
             beginning: false,
             follow: false,
             pid: 0,
@@ -83,12 +84,11 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
     let matches = app.get_matches_from(args);
 
     settings.follow = matches.is_present(options::FOLLOW);
-    if settings.follow {
-        if let Some(n) = matches.value_of(options::SLEEP_INT) {
-            let parsed: Option<u32> = n.parse().ok();
-            if let Some(m) = parsed {
-                settings.sleep_msec = m * 1000
-            }
+
+    if let Some(s) = matches.value_of(options::SLEEP_INT) {
+        settings.sleep_sec = match s.parse::<f32>() {
+            Ok(s) => Duration::from_secs_f32(s),
+            Err(_) => crash!(1, "invalid number of seconds: {}", s.quote()),
         }
     }
 
@@ -297,7 +297,7 @@ fn follow<T: BufRead>(readers: &mut [(T, &String)], settings: &Settings) {
     let mut process = platform::ProcessChecker::new(settings.pid);
 
     loop {
-        sleep(Duration::new(0, settings.sleep_msec * 1000));
+        sleep(settings.sleep_sec);
 
         let pid_is_dead = !read_some && settings.pid != 0 && process.is_dead();
         read_some = false;
diff --git a/tests/by-util/test_tail.rs b/tests/by-util/test_tail.rs
index 26d8106f0..c2984968d 100644
--- a/tests/by-util/test_tail.rs
+++ b/tests/by-util/test_tail.rs
@@ -326,6 +326,16 @@ fn test_negative_indexing() {
 #[test]
 fn test_sleep_interval() {
     new_ucmd!().arg("-s").arg("10").arg(FOOBAR_TXT).succeeds();
+    new_ucmd!().arg("-s").arg(".1").arg(FOOBAR_TXT).succeeds();
+    new_ucmd!().arg("-s.1").arg(FOOBAR_TXT).succeeds();
+    new_ucmd!().arg("-s").arg("-1").arg(FOOBAR_TXT).fails();
+    new_ucmd!()
+        .arg("-s")
+        .arg("1..1")
+        .arg(FOOBAR_TXT)
+        .fails()
+        .stderr_contains("invalid number of seconds: '1..1'")
+        .code_is(1);
 }
 
 /// Test for reading all but the first NUM bytes: `tail -c +3`.