Added all given material for exercise 2

12 files changed, 428 insertions, 0 deletions

diff --git a/02_exercise/beispiele/dup/Makefile b/02_exercise/beispiele/dup/Makefile
new file mode 100644
index 0000000..0f73ac4
--- /dev/null
+++ b/02_exercise/beispiele/dup/Makefile
@@ -0,0 +1,18 @@
+#!/usr/bin/make
+.SUFFIXES:
+
+CFLAGS = -c -Os -Wall -Werror
+
+%.o: %.c
+	$(CC) $(CFLAGS) $^ -o $@
+
+%: %.o
+	$(CC) -o $@ $^
+
+all: dup
+
+run: all
+	./dup
+
+clean:
+	$(RM) $(RMFILES) dup
diff --git a/02_exercise/beispiele/dup/dup.c b/02_exercise/beispiele/dup/dup.c
new file mode 100644
index 0000000..ea3c5a6
--- /dev/null
+++ b/02_exercise/beispiele/dup/dup.c
@@ -0,0 +1,51 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/* https://www.youtube.com/watch?v=gaXigSu72A4 */
+static inline void die(const char* msg) {
+	perror(msg);
+	exit(EXIT_FAILURE);
+}
+
+int main(int argc, char **argv) {
+	int pdes[2];
+	pid_t child;
+ 	
+	if (pipe(pdes) < 0)
+		die("pipe()");
+ 	
+	if ((child = fork()) < 0)
+		die("fork()");
+ 	
+	if (child == 0) {
+		/* child process */
+      	close(pdes[0]);
+		close(1);       /* close stdout */
+		
+		if (dup(pdes[1]) < 0)
+			die("dup()");
+		
+		/* now stdout and pdes[1] are equivalent (dup returns lowest free descriptor) */
+		if (execlp("cat", "cat", "/etc/passwd", NULL) < 0)
+			die("execlp()");
+		
+		exit(EXIT_SUCCESS);
+	}
+	else {
+		/* parent process */
+		close(0);       /* close stdin */
+		close(pdes[1]);
+		
+		if (dup(pdes[0]) < 0)
+			die("dup()");
+		
+		/* now stdin and pdes[0] are equivalent (dup returns lowest free descriptor) */
+		if (execlp("wc", "wc", "-l", NULL) < 0)
+			die("execlp()");
+		
+		exit(EXIT_SUCCESS);
+	}
+	
+	return 0;
+}
diff --git a/02_exercise/beispiele/fork_example/Makefile b/02_exercise/beispiele/fork_example/Makefile
new file mode 100644
index 0000000..8f69ed9
--- /dev/null
+++ b/02_exercise/beispiele/fork_example/Makefile
@@ -0,0 +1,18 @@
+#!/usr/bin/make
+.SUFFIXES:
+
+CFLAGS = -c -Os -Wall -Werror
+
+%.o: %.c
+	$(CC) $(CFLAGS) $^ -o $@
+
+%: %.o
+	$(CC) -o $@ $^
+
+all: fork
+
+run: all
+	./fork
+
+clean:
+	$(RM) $(RMFILES) fork
diff --git a/02_exercise/beispiele/fork_example/fork.c b/02_exercise/beispiele/fork_example/fork.c
new file mode 100644
index 0000000..7377b0f
--- /dev/null
+++ b/02_exercise/beispiele/fork_example/fork.c
@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+int main(void) {
+	pid_t proc_id;
+	int status = 0;
+	
+	proc_id = fork();
+	
+	if (proc_id < 0) {
+		fprintf(stderr, "fork error\n");
+		fflush(stderr);
+		return EXIT_FAILURE;
+	}
+	
+	if (proc_id == 0) {
+		/* child process */
+		printf("[child]  process id: %d\n", (int) getpid());
+		
+		char* args[] = {"sleep", "1", NULL};
+		execvp(args[0], args);
+		exit(-1);
+	}
+	else {
+		/* parent */
+		printf("[parent] process id: %d\n", (int) getpid());
+		pid_t child_id = wait(&status);
+		
+		printf("[parent] child %d returned: %d\n",
+		        child_id, WEXITSTATUS(status));
+	}
+	
+	return EXIT_SUCCESS;
+}
diff --git a/02_exercise/beispiele/fork_signal/Makefile b/02_exercise/beispiele/fork_signal/Makefile
new file mode 100644
index 0000000..499b8cb
--- /dev/null
+++ b/02_exercise/beispiele/fork_signal/Makefile
@@ -0,0 +1,19 @@
+#!/usr/bin/make
+.SUFFIXES:
+
+CFLAGS = -c -O0
+
+%.o: %.c
+	$(CC) $(CFLAGS) $^ -o $@
+
+%: %.o
+	$(CC) -o $@ $^
+
+all: fork signal
+
+run: all
+	./fork 10
+	./signal
+
+clean:
+	$(RM) $(RMFILES) fork signal
diff --git a/02_exercise/beispiele/fork_signal/fork.c b/02_exercise/beispiele/fork_signal/fork.c
new file mode 100644
index 0000000..b144577
--- /dev/null
+++ b/02_exercise/beispiele/fork_signal/fork.c
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+int main(int argc, const char* argv[]) {
+	pid_t pid;
+	int h;
+	int count;
+	
+	if (argc < 2) {
+		printf("Usage: ./fork process#\n");
+		return 0;
+	}
+	
+	count = atoi(argv[1]) - 1;
+	printf("Process#: %d\n", count + 1);
+	printf("Parent started\n");
+	
+	pid = 1;
+	for (h = 0; h < count; ++h) {
+		if ((pid = fork()) < 0)
+			printf("fork error\n");
+		else if (pid == 0) {
+			printf("Child %d started\n", h);
+			sleep(1);
+			printf("Child %d finished\n", h);
+			exit(0);
+		}
+	}
+	
+	printf("Parent waiting\n");
+	for (h = 0; h < count; ++h) {
+		wait(NULL);
+	}
+	printf("Parent finished\n");
+	return EXIT_SUCCESS;
+}
diff --git a/02_exercise/beispiele/fork_signal/signal.c b/02_exercise/beispiele/fork_signal/signal.c
new file mode 100644
index 0000000..500d2e1
--- /dev/null
+++ b/02_exercise/beispiele/fork_signal/signal.c
@@ -0,0 +1,21 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+
+void sig_handler(int signo) {
+	const char msg[] = "Speicherzugriffsfehler!\n";
+	write(2, msg, sizeof(msg) - 1);
+	exit(-1);
+}
+
+int main(void) {
+	if (signal(SIGSEGV, sig_handler) == SIG_ERR) {
+		perror("signal");
+		exit(-1);
+	}
+	
+	int array[1] = {0};
+	array[1000000] = 3;
+	return 0;
+}
diff --git a/02_exercise/beispiele/pipe_bidirect/Makefile b/02_exercise/beispiele/pipe_bidirect/Makefile
new file mode 100644
index 0000000..361ac97
--- /dev/null
+++ b/02_exercise/beispiele/pipe_bidirect/Makefile
@@ -0,0 +1,19 @@
+#!/usr/bin/make
+.SUFFIXES:
+
+CFLAGS = -c -Os -Wall -Werror
+
+%.o: %.c
+	$(CC) $(CFLAGS) $^ -o $@
+
+%: %.o
+	$(CC) -o $@ $^
+
+all: pingpong
+
+run: all
+	@echo "writing into log.txt; stop execution with CTRL+C"
+	./pingpong
+
+clean:
+	$(RM) $(RMFILES) pingpong
diff --git a/02_exercise/beispiele/pipe_bidirect/log.txt b/02_exercise/beispiele/pipe_bidirect/log.txt
new file mode 100644
index 0000000..fbdc2c7
--- /dev/null
+++ b/02_exercise/beispiele/pipe_bidirect/log.txt
@@ -0,0 +1,5 @@
+[15234]: ping
+[15233]: pong
+[15234]: ping
+[15233]: pong
+Programmabbruch durch Nutzer
diff --git a/02_exercise/beispiele/pipe_bidirect/pingpong.c b/02_exercise/beispiele/pipe_bidirect/pingpong.c
new file mode 100644
index 0000000..ac5eb1c
--- /dev/null
+++ b/02_exercise/beispiele/pipe_bidirect/pingpong.c
@@ -0,0 +1,124 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+static int split(int fd[2]);
+static int redir(int fd, const char* file);
+static void sig_handler(int sig);
+
+static int parent;
+
+int main(void) {
+	ssize_t bytes;
+	char buf[256];
+	int fd[2];
+	
+	// disable buffering for stdout
+	setvbuf(stdout, NULL, _IONBF, 0);
+	
+	// redirect stdout to write into a file
+	if (redir(1, "log.txt") < 0) {
+		perror("redir()");
+		exit(-1);
+	}
+	
+	// install the signal handler for Ctrl+C
+	if (signal(SIGINT, sig_handler) == SIG_ERR) {
+		perror("signal()");
+		exit(-1);
+	}
+	
+	// split processes and assign file descriptors for communication
+	switch (split(fd)) {
+	case -1: // error
+		exit(-1);
+		
+	case 0:  // child
+		while ((bytes = read(fd[0], buf, sizeof(buf))) > 0) {
+			printf("[%u]: %s\n", getpid(), buf);
+			sleep(1);
+			write(fd[1], "pong", 5);
+		}
+		break;
+		
+	case 1:  // parent
+		parent = 1;
+		write(fd[1], "ping", 5);
+		while ((bytes = read(fd[0], buf, sizeof(buf))) > 0) {
+			printf("[%u]: %s\n", getpid(), buf);
+			sleep(1);
+			write(fd[1], "ping", 5);
+		}
+		break;
+	}
+	
+	// close the file descriptors
+	close(fd[0]);
+	close(fd[1]);
+	
+	return 0;
+}
+
+int split(int fd[2]) {
+	int pfd[2][2];
+	
+	if (pipe(pfd[0]) < 0) {
+		perror("pipe()");
+		goto err_pipe1;
+	}
+	
+	if (pipe(pfd[1]) < 0) {
+		perror("pipe()");
+		goto err_pipe2;
+	}
+	
+	switch (fork()) {
+	case -1:
+		perror("fork()");
+		goto err_fork;
+		
+	case 0:  // child process
+		close(pfd[0][1]);  // close write for child
+		close(pfd[1][0]);  // close read for parent
+		fd[0] = pfd[0][0]; // keep read for child
+		fd[1] = pfd[1][1]; // keep write for parent
+		return 0;
+		
+	default: // parent process
+		close(pfd[1][1]);  // close write for parent
+		close(pfd[0][0]);  // close read for child
+		fd[0] = pfd[1][0]; // keep read for parent
+		fd[1] = pfd[0][1]; // keep write for child
+		return 1;
+	}
+	
+err_fork:
+	close(pfd[1][0]);
+	close(pfd[1][1]);
+err_pipe2:
+	close(pfd[0][0]);
+	close(pfd[0][1]);
+err_pipe1:
+	return -1;
+}
+
+int redir(int fd, const char* file) {
+	int fd2 = open(file, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+	
+	if (fd2 < 0)
+		return -1;
+	
+	dup2(fd2, fd);
+	close(fd2);
+	
+	return 0;
+}
+
+void sig_handler(int sig) {
+	if (parent) {
+		const char msg[] = "Programmabbruch durch Nutzer\n";
+		write(1, msg, sizeof(msg) - 1);
+	}
+	exit(0);
+}
diff --git a/02_exercise/beispiele/pipe_example/Makefile b/02_exercise/beispiele/pipe_example/Makefile
new file mode 100644
index 0000000..d69473e
--- /dev/null
+++ b/02_exercise/beispiele/pipe_example/Makefile
@@ -0,0 +1,18 @@
+#!/usr/bin/make
+.SUFFIXES:
+
+CFLAGS = -c -Os -Wall -Werror
+
+%.o: %.c
+	$(CC) $(CFLAGS) $^ -o $@
+
+%: %.o
+	$(CC) -o $@ $^
+
+all: pipe
+
+run: all
+	./pipe
+
+clean:
+	$(RM) $(RMFILES) pipe
diff --git a/02_exercise/beispiele/pipe_example/pipe.c b/02_exercise/beispiele/pipe_example/pipe.c
new file mode 100644
index 0000000..3589c63
--- /dev/null
+++ b/02_exercise/beispiele/pipe_example/pipe.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define BUF_SIZE 32
+
+int pipe_fds[2];
+
+void term(const char *msg) {
+	if (msg) {
+		fprintf(stderr, "Error: %s\n", msg);
+		fflush(stderr);
+	}
+	
+	int close_fail = 0;
+	int ret = close(pipe_fds[0]);
+	
+	if (ret < 0) {
+		fprintf(stderr, "Error: Couldn't close reading end of pipe\n");
+		fflush(stderr);
+		close_fail = 1;
+	}
+	
+	ret = close(pipe_fds[1]);
+	
+	if (ret < 0) {
+		fprintf(stderr, "Error: Couldn't close writing end of pipe\n");
+		fflush(stderr);
+		close_fail = 1;
+	}
+	
+	exit((msg || close_fail) ? EXIT_FAILURE : EXIT_SUCCESS);
+}
+
+int main(void) {
+	int ret = pipe(pipe_fds);
+	
+	if (ret < 0)
+		term("Couldn't create pipe");
+	
+	char out_buf[] = "hello";
+	ret = write(pipe_fds[1], out_buf, strlen(out_buf) + 1);
+	
+	if (ret < 0)
+		term("Couldn't write to pipe");
+	
+	printf("send msg: %s\n", out_buf);
+	
+	char in_buf[BUF_SIZE];
+	memset(in_buf, 0, BUF_SIZE);
+	
+	ret = read(pipe_fds[0], in_buf, BUF_SIZE - 1);
+	
+	if (ret < 0)
+		term("Couldn't read from pipe");
+	
+	printf("recv msg: %s\n", in_buf);
+	return 0;
+}