ostep: add hw5

ostep/hw5/Makefile

@@ -1,4 +1,10 @@
-TARGETS :=	hw5_1
+TARGETS :=	hw5_1	\
+		hw5_2	\
+		hw5_3	\
+		hw5_5	\
+		hw5_6	\
+		hw5_7	\
+		hw5_8
 
 all: $(TARGETS)
 

ostep/hw5/hw5_2.c

@@ -0,0 +1,49 @@
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+const char	default_path[] = "hello.txt";
+
+int
+main(int argc, char *argv[])
+{
+	char	 buf[2] = {0x41, 0x0a};
+	char	*pathname = (char *)default_path;
+	int	 fd = -1;
+
+	if (argc > 1) {
+		pathname = argv[1];
+	}
+
+	fd = open(pathname, O_WRONLY|O_CREAT, S_IWUSR|S_IRUSR);
+	if (fd == -1) {
+		perror("open");
+		exit(1);
+	}
+
+	pid_t	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		exit(1);
+	}
+	else if (pid > 0) {
+		for (int i = 0; i < 5; i++) {
+			write(fd, buf, 2);
+			sleep(1);
+		}
+	}
+	else {
+		buf[0] = 0x42;
+		for (int i = 0; i < 5; i++) {
+			write(fd, buf, 2);
+			sleep(1);
+		}
+	}
+
+	close(fd);
+	exit(0);
+}
+

ostep/hw5/hw5_3.c

@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int
+main(void)
+{
+	int	pipefd[2];
+
+	if (pipe(pipefd) == -1) {
+		perror("pipe");
+		exit(1);
+	}
+
+	pid_t	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		exit(1);
+	}
+	else if (pid > 0) {
+		close(pipefd[1]);
+
+		char	buf[1];
+		read(pipefd[0], buf, 1);
+		printf("goodbye\n");	
+	}
+	else {
+		sleep(1);
+		close(pipefd[0]);
+
+		printf("hello\n");
+		close(pipefd[1]);
+	}
+}

ostep/hw5/hw5_5.c

@@ -0,0 +1,33 @@
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int
+main(void)
+{
+	int	status = 0;
+
+	pid_t	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		exit(EXIT_FAILURE);
+	}
+	else if (pid > 0) {
+		wait(&status);
+		if (!WIFEXITED(status)) {
+			fprintf(stderr, "child exited due to an error\n");
+		}
+		printf("goodbye: %d\n", status);
+	}
+	else {
+		wait(&status);
+		if (!WIFEXITED(status)) {
+			fprintf(stderr, "child exited due to an error\n");
+		}
+		printf("hello: %d\n", status);
+	}
+
+	exit(EXIT_SUCCESS);
+}

ostep/hw5/hw5_6.c

@@ -0,0 +1,29 @@
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int
+main(void)
+{
+	int	status = 0;
+
+	pid_t	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		exit(EXIT_FAILURE);
+	}
+	else if (pid > 0) {
+		waitpid(pid, &status, 0);
+		if (!WIFEXITED(status)) {
+			fprintf(stderr, "child exited due to an error\n");
+		}
+		printf("goodbye: %d\n", status);
+	}
+	else {
+		printf("hello: %d\n", status);
+	}
+
+	exit(EXIT_SUCCESS);
+}

ostep/hw5/hw5_7.c

@@ -0,0 +1,27 @@
+#include <sys/wait.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int
+main(void)
+{
+	pid_t	pid;
+
+	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		exit(1);
+	}
+	// child
+	else if (pid > 0) {
+		close(STDOUT_FILENO);
+		printf("screaming into the void...\n");
+	}
+	else {
+		wait(NULL);
+		printf("the darkness\n");
+	}
+
+	exit(EXIT_SUCCESS);
+}

ostep/hw5/hw5_8.c

@@ -0,0 +1,85 @@
+#include <sys/wait.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int	pipefd[2];
+
+int
+main(void)
+{
+	if (pipe(pipefd) != 0) {
+		perror("pipe");
+		return EXIT_FAILURE;
+	}
+	int	pwrite = pipefd[1];
+	int	pread = pipefd[0];
+
+	pid_t	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		return EXIT_FAILURE;
+	}
+	/* the first child */
+	else if (pid == 0) {
+		/*
+		 * Close standard output and reassign it to the pipe.
+		 * The close is done automagically by dup2.
+		 */
+		dup2(pwrite, STDOUT_FILENO);
+
+		/* Close unnecessary pipe read file descriptor. */
+		close(pread);
+
+		/* Now we do the thing. */
+		printf("Hello, world.\n");
+
+		/* ¡Adios! */
+		return EXIT_SUCCESS;
+	}
+	
+	/*
+	 * We are now in the parent. We must fork again, and do the
+	 * child dance.
+	 */
+	if ((pid = fork()) < 0) {
+		perror("fork");
+		return EXIT_FAILURE;
+	}
+	/* the second of the children */
+	else if (pid == 0) {
+		/* Close standard input and reassign it to the pipe. */
+		dup2(pread, STDIN_FILENO);
+
+		/* Close unnecessary pipe write file descriptor. */
+		close(pwrite);
+
+		/* Read the thing. */
+		char	data[16];
+		ssize_t	rl;
+
+		memset(data, 0, 16);
+		rl = read(STDIN_FILENO, data, 15);
+		if (rl < 1) {
+			perror("read");
+			return EXIT_FAILURE;
+		}
+
+		printf("%s", data);
+		return EXIT_SUCCESS;
+	}
+
+	/* wait for the children to die so we can reap them */
+	/* there are two, they should drop dead on their own. */
+	int status1, status2;
+	waitpid(-1, &status1, 0);
+	waitpid(-1, &status2, 0);
+
+	if (WIFEXITED(status1) && WIFEXITED(status2)) {
+		printf("Goodbye.\n");
+		return EXIT_SUCCESS;
+	}
+	fprintf(stderr, "At least one child died abnormally.\n");
+	return EXIT_FAILURE;
+}