Userland: Add pgrep

Userland/Utilities/pgrep.cpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2021, Aziz Berkay Yesilyurt <abyesilyurt@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/QuickSort.h>
+#include <AK/Vector.h>
+#include <LibCore/ArgsParser.h>
+#include <LibCore/ProcessStatisticsReader.h>
+#include <LibRegex/Regex.h>
+
+int main(int argc, char** argv)
+{
+    if (pledge("stdio rpath", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    bool case_insensitive = false;
+    bool invert_match = false;
+    char const* pattern = nullptr;
+
+    Core::ArgsParser args_parser;
+    args_parser.add_option(case_insensitive, "Make matches case-insensitive", nullptr, 'i');
+    args_parser.add_option(invert_match, "Select non-matching lines", "invert-match", 'v');
+    args_parser.add_positional_argument(pattern, "Process name to search for", "process-name");
+    args_parser.parse(argc, argv);
+
+    PosixOptions options {};
+    if (case_insensitive)
+        options |= PosixFlags::Insensitive;
+
+    Regex<PosixExtended> re(pattern, options);
+    if (re.parser_result.error != Error::NoError) {
+        return 1;
+    }
+
+    auto processes = Core::ProcessStatisticsReader::get_all();
+    if (!processes.has_value())
+        return 1;
+
+    Vector<pid_t> matches;
+    for (auto& it : processes.value()) {
+        auto result = re.match(it.name, PosixFlags::Global);
+        if (result.success ^ invert_match) {
+            matches.append(it.pid);
+        }
+    }
+
+    quick_sort(matches);
+
+    for (auto& match : matches) {
+        outln("{}", match);
+    }
+
+    return 0;
+}