uucore: Support parsing real-time signals.

This allows `timeout -s`, `kill -s`, and `env --{block,default,ignore}-signal` to recognize and handle signals of the forms `RTMIN`, `RTMIN+n`, `RTMAX`, and `RTMAX-n`, consistent with the behaviour of GNU coreutils.

Author: aweinstock

src/uucore/src/lib/features/signals.rs

@@ -400,7 +400,52 @@ pub fn signal_by_name_or_value(signal_name_or_value: &str) -> Option<usize> {
     }
     let signal_name = signal_name_upcase.trim_start_matches("SIG");
 
-    ALL_SIGNALS.iter().position(|&s| s == signal_name)
+    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
+    return try_parse_sigrt(signal_name_or_value)
+        .or_else(|| ALL_SIGNALS.iter().position(|&s| s == signal_name));
+    #[cfg(not(any(target_os = "linux", target_os = "freebsd")))]
+    return ALL_SIGNALS.iter().position(|&s| s == signal_name);
+}
+
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+/// Parses signals of the form RTMIN(+[0-9]\+)?|RTMAX(-[0-9]\+)?
+fn try_parse_sigrt(signal_name: &str) -> Option<usize> {
+    if crate::os::is_wsl() {
+        return None;
+    }
+    if let Some(rest) = signal_name.strip_prefix("RTMIN") {
+        if rest.is_empty() {
+            Some(libc::SIGRTMIN() as usize)
+        } else if let Some(rest) = rest.strip_prefix("+")
+            && let Ok(offset) = rest.parse::<usize>()
+        {
+            let value = libc::SIGRTMIN() as usize + offset;
+            if value <= libc::SIGRTMAX() as usize {
+                Some(value)
+            } else {
+                None
+            }
+        } else {
+            None
+        }
+    } else if let Some(rest) = signal_name.strip_prefix("RTMAX") {
+        if rest.is_empty() {
+            Some(libc::SIGRTMAX() as usize)
+        } else if let Some(rest) = rest.strip_prefix("-")
+            && let Ok(offset) = rest.parse::<usize>()
+        {
+            let value = libc::SIGRTMAX() as usize - offset;
+            if value >= libc::SIGRTMIN() as usize {
+                Some(value)
+            } else {
+                None
+            }
+        } else {
+            None
+        }
+    } else {
+        None
+    }
 }
 
 /// Returns true if the given number is a valid signal number.

tests/by-util/test_kill.rs

@@ -2,7 +2,7 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
-// spell-checker:ignore IAMNOTASIGNAL RTMAX RTMIN SIGRTMAX
+// spell-checker:ignore IAMNOTASIGNAL RTMAX RTMIN SIGRTMAX SIGRT SIGRTMIN SIGRTMAX
 use regex::Regex;
 use std::os::unix::process::ExitStatusExt;
 use std::process::{Child, Command};
@@ -493,3 +493,18 @@ fn test_kill_signal_only_no_pid() {
         .fails()
         .stderr_contains("no process ID specified");
 }
+
+#[test]
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+fn test_kill_with_signal_sigrt() {
+    if !uucore::os::is_wsl() {
+        for signal in &["SIGRTMIN", "SIGRTMIN+1", "SIGRTMAX", "SIGRTMAX-1"] {
+            let target = Target::new();
+            new_ucmd!()
+                .arg("-s")
+                .arg(signal)
+                .arg(format!("{}", target.pid()))
+                .succeeds();
+        }
+    }
+}

tests/by-util/test_timeout.rs

@@ -3,7 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore dont
+// spell-checker:ignore dont sigrt sigrtmin sigrtmax
 
 use rstest::rstest;
 use std::time::Duration;
@@ -286,3 +286,22 @@ fn test_foreground_signal0_kill_after() {
         .args(&["--foreground", "-s0", "-k.1", ".1", "sleep", "10"])
         .fails_with_code(137);
 }
+
+#[test]
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+fn test_timeout_sigrt() {
+    if !uucore::os::is_wsl() {
+        new_ucmd!()
+            .args(&["-s", "SIGRTMIN", "0.1", "sleep", "2"])
+            .succeeds();
+        new_ucmd!()
+            .args(&["-s", "SIGRTMIN+1", "0.1", "sleep", "2"])
+            .succeeds();
+        new_ucmd!()
+            .args(&["-s", "SIGRTMAX", "0.1", "sleep", "2"])
+            .succeeds();
+        new_ucmd!()
+            .args(&["-s", "SIGRTMAX-1", "0.1", "sleep", "2"])
+            .succeeds();
+    }
+}