Feature/pidof (#31)

* Added killall command

* Fixed feedbacks of awesomekling

* Implemented pidof program and helper to parse arguments called ArgsParser.

* Fixed feedbacks in pidof implem.

Fixes #26

Userland/pidof.cpp

@@ -0,0 +1,89 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <LibCore/CFile.h>
+#include <AK/AKString.h>
+#include <AK/Vector.h>
+#include <AK/ArgsParser.h>
+
+static int pid_of(const String& process_name, bool single_shot, bool omit_pid, pid_t pid)
+{
+    bool displayed_at_least_one = false;
+
+    CFile file("/proc/all");
+    if (!file.open(CIODevice::ReadOnly)) {
+	fprintf(stderr, "pidof failed to open /proc/all\n");
+	return 2;
+    }
+
+    for (;;) {
+	auto line = file.read_line(1024);
+		
+	if (line.is_empty())
+	    break;
+
+	auto chomped = String((const char*)line.pointer(), line.size() - 1, Chomp);
+	auto parts = chomped.split_view(',');
+
+	if (parts.size() < 18)
+	    break;
+
+	bool ok = false;
+	pid_t current_pid = parts[0].to_uint(ok);
+	String name = parts[11];
+
+	if (!ok) {
+	    fprintf(stderr, "pidof failed : couldn't convert %s to a valid pid\n", parts[0].characters());
+	    return 3;
+	}
+		
+	if (name == process_name) {	
+	    if (!omit_pid || (omit_pid && current_pid != pid)) {
+		printf("%d ", current_pid);
+		displayed_at_least_one = true;
+
+		if (single_shot)
+		    break;
+	    }
+	}
+    }
+
+    if (displayed_at_least_one)
+	printf("\n");
+
+    return 0;
+}
+
+int main(int argc, char** argv)
+{
+    AK::ArgsParser args_parser("pidof", "-");
+    
+    args_parser.add_arg("s", "Single shot - this instructs the program to only return one pid", false);
+    args_parser.add_arg("o", "pid", "Tells pidof to omit processes with that pid. The special pid %PPID can be used to name the parent process of the pidof program.", false);
+    
+    AK::ArgsParserResult args = args_parser.parse(argc, (const char**)argv);
+    
+    bool s_arg = args.is_present("s");
+    bool o_arg = args.is_present("o");
+    pid_t pid = 0;
+    
+    if (o_arg) {
+        bool ok = false;
+        String pid_str = args.get("o");
+
+	if (pid_str == "%PPID")
+	    pid = getppid();
+	else
+	    pid = pid_str.to_uint(ok);
+    }
+    
+    // We should have one single value : the process name
+    Vector<String> values = args.get_single_values();
+    if (values.size() == 0) {
+	args_parser.print_usage();
+        return 0;
+    }
+    
+    return pid_of(values[0], s_arg, o_arg, pid);
+}