pgrep, pkill: Add check for pattern length

pidwait already has a check for this, copy it to the common
process_matcher implementation.

Some tests need adjustment to not use such long fake names.

src/uu/pgrep/src/process_matcher.rs

@@ -78,6 +78,12 @@ pub fn get_match_settings(matches: &ArgMatches) -> UResult<Settings> {
         ));
     }
 
+    if !settings.full && pattern.len() >= 15 {
+        let msg = format!("pattern that searches for process name longer than 15 characters will result in zero matches\n\
+                           Try `{} -f' option to match against the complete command line.", uucore::util_name());
+        return Err(USimpleError::new(1, msg));
+    }
+
     Ok(settings)
 }
 

tests/by-util/test_pgrep.rs

@@ -31,7 +31,7 @@ fn test_no_args() {
 #[test]
 fn test_non_matching_pattern() {
     new_ucmd!()
-        .arg("THIS_PATTERN_DOES_NOT_MATCH")
+        .arg("NONMATCHING")
         .fails()
         .code_is(1)
         .no_output();
@@ -368,3 +368,13 @@ fn test_invalid_signal() {
         .fails()
         .stderr_contains("Unknown signal 'foo'");
 }
+
+#[test]
+#[cfg(target_os = "linux")]
+fn test_too_long_pattern() {
+    new_ucmd!()
+        .arg("THIS_IS_OVER_16_CHARS")
+        .fails()
+        .code_is(1)
+        .stderr_contains("pattern that searches for process name longer than 15 characters will result in zero matches");
+}

tests/by-util/test_pkill.rs

@@ -20,7 +20,7 @@ fn test_no_args() {
 #[test]
 fn test_non_matching_pattern() {
     new_ucmd!()
-        .arg("THIS_PATTERN_DOES_NOT_MATCH")
+        .arg("NONMATCHING")
         .fails()
         .code_is(1)
         .no_output();
@@ -60,3 +60,13 @@ fn test_inverse() {
 fn test_help() {
     new_ucmd!().arg("--help").succeeds();
 }
+
+#[test]
+#[cfg(target_os = "linux")]
+fn test_too_long_pattern() {
+    new_ucmd!()
+        .arg("THIS_IS_OVER_16_CHARS")
+        .fails()
+        .code_is(1)
+        .stderr_contains("pattern that searches for process name longer than 15 characters will result in zero matches");
+}