chore: migrate src to solutions

solutions/01_environment/process/process.c

@@ -0,0 +1,133 @@
+/**
+ * Copyright 2015 University of Applied Sciences Western Switzerland / Fribourg
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * 
+ * Module:	MA-CSEL1 - Building Embedded Systems under Linux
+ *
+ * Abstract: 	Introduction to the Embedded Linux Development Environment
+ *
+ * Purpose:	This module implements a simple application to be launched from
+ *		/etc/inttab.
+ *		-->> tracing with syslog
+ *
+ * Autĥor:	Daniel Gachet
+ * Date:	28.08.2015
+ */
+#define _XOPEN_SOURCE 600
+#define _DEFAULT_SOURCE
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <grp.h>
+#include <pwd.h>
+#include <signal.h>
+#include <syslog.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+#define UNUSED(x) (void)(x)
+
+static int signal_catched = 0; 
+
+static void catch_signal (int signal)
+{
+	syslog (LOG_INFO, "signal=%d catched\n", signal);
+	signal_catched++;
+}
+
+int main(int argc, char* argv[])
+{
+	UNUSED(argc); UNUSED(argv);
+	
+	// daemon's steps 1 to 3 skipt
+
+	// 4. capture all required signals
+	struct sigaction act = {.sa_handler = catch_signal,};
+	sigaction (SIGHUP,  &act, NULL);  //  1 - hangup
+	sigaction (SIGINT,  &act, NULL);  //  2 - terminal interrupt
+	sigaction (SIGQUIT, &act, NULL);  //  3 - terminal quit
+	sigaction (SIGABRT, &act, NULL);  //  6 - abort
+	sigaction (SIGTERM, &act, NULL);  // 15 - termination
+	sigaction (SIGTSTP, &act, NULL);  // 19 - terminal stop signal
+
+	// 5. update file mode creation mask
+	umask(0027);
+
+	// 6. change working directory to appropriate place
+	if (chdir ("/") == -1) {
+		syslog (LOG_ERR, "ERROR while changing to working directory"); 
+		exit (1);
+	}
+
+	// 7. close all open file descriptors
+	for (int fd = sysconf(_SC_OPEN_MAX); fd >= 0; fd--) {
+		close (fd);
+	}
+
+	// 8. redirect stdin, stdout and stderr to /dev/null
+	if (open ("/dev/null", O_RDWR) != STDIN_FILENO) {
+		syslog (LOG_ERR, "ERROR while opening '/dev/null' for stdin");
+		exit (1);
+	}
+	if (dup2 (STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO) {
+		syslog (LOG_ERR, "ERROR while opening '/dev/null' for stdout");
+		exit (1);
+	}
+	if (dup2 (STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO) {
+		syslog (LOG_ERR, "ERROR while opening '/dev/null' for stderr");
+		exit (1);
+	}
+
+	// 9. option: open syslog for message logging
+	openlog (NULL, LOG_NDELAY | LOG_PID, LOG_DAEMON); 
+	syslog (LOG_INFO, "Daemon has started...");
+ 
+	// 10. option: get effective user and group id for appropriate's one
+	struct passwd* pwd = getpwnam ("daemon");
+	if (pwd == 0) {
+		syslog (LOG_ERR, "ERROR while reading daemon password file entry");
+		exit (1);
+	}
+
+	// 11. option: change root directory
+	if (chroot (".") == -1) {
+		syslog (LOG_ERR, "ERROR while changing to new root directory");
+		exit (1);
+	}
+
+	// 12. option: change effective user and group id for appropriate's one
+	if (setegid (pwd->pw_gid) == -1) {
+		syslog (LOG_ERR, "ERROR while setting new effective group id");
+		exit (1);
+	}
+	if (seteuid (pwd->pw_uid) == -1) {
+		syslog (LOG_ERR, "ERROR while setting new effective user id");
+		exit (1);
+	}
+ 
+	// 13. implement daemon body...
+	int t = 30;
+	do {
+		t = sleep(t);
+	} while (t > 0);
+
+	syslog (LOG_INFO, "daemon stopped. Number of signals catched=%d\n", signal_catched);
+	closelog();
+
+	return 0;
+}