9 files changed, 309 insertions, 0 deletions
diff --git a/Year 3/System programming/Practice05/ex1.c b/Year 3/System programming/Practice05/ex1.c
new file mode 100644
index 0000000..4d9966d
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex1.c
@@ -0,0 +1,34 @@
+#include <unistd.h> // fork, write, close, sleep
+#include <fcntl.h> // open
+#include <stdio.h> // perror
+
+int main(int argc, char* argv[]) {
+	pid_t f = fork();
+	int file = open("test.txt", O_WRONLY);
+	if (file < 0) {
+		perror("open");
+		return 1;
+	}
+
+	if (f == 0) { // in child
+		char buf = 'c';
+		for (int i = 0; i < 5; i++) {
+			sleep(2);
+			if(write(file, &buf, 1) < 0) {
+				perror("write");
+				return 2;
+			}
+		}
+	}
+	else {
+		char buf = 'p';
+		for (int i = 0; i < 5; i++) {
+			if(write(file, &buf, 1) < 0) {
+				perror("write");
+				return 3;
+			}
+			sleep(1);
+		}
+	}
+	close(file);
+}
diff --git a/Year 3/System programming/Practice05/ex2.c b/Year 3/System programming/Practice05/ex2.c
new file mode 100644
index 0000000..85ce0dd
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex2.c
@@ -0,0 +1,34 @@
+#include <unistd.h> // fork, write, close, sleep
+#include <fcntl.h> // open
+#include <stdio.h> // perror
+
+int main(int argc, char* argv[]) {
+	int file = open("test.txt", O_WRONLY);
+	if (file < 0) {
+		perror("open");
+		return 1;
+	}
+	pid_t f = fork();
+
+	if (f == 0) { // in child
+		char buf = 'c';
+		for (int i = 0; i < 5; i++) {
+			sleep(2);
+			if(write(file, &buf, 1) < 0) {
+				perror("write");
+				return 2;
+			}
+		}
+	}
+	else {
+		char buf = 'p';
+		for (int i = 0; i < 5; i++) {
+			if(write(file, &buf, 1) < 0) {
+				perror("write");
+				return 3;
+			}
+			sleep(1);
+		}
+	}
+	close(file);
+}
diff --git a/Year 3/System programming/Practice05/ex3.c b/Year 3/System programming/Practice05/ex3.c
new file mode 100644
index 0000000..7374411
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex3.c
@@ -0,0 +1,34 @@
+#include <unistd.h> // fork, write, close, sleep
+#include <fcntl.h> // open
+#include <stdio.h> // perror
+
+int main(int argc, char* argv[]) {
+	pid_t f = fork();
+	int file = open("test.txt", O_WRONLY | O_APPEND);
+	if (file < 0) {
+		perror("open");
+		return 1;
+	}
+
+	if (f == 0) { // in child
+		char buf = 'c';
+		for (int i = 0; i < 5; i++) {
+			sleep(2);
+			if(write(file, &buf, 1) < 0) {
+				perror("write");
+				return 2;
+			}
+		}
+	}
+	else {
+		char buf = 'p';
+		for (int i = 0; i < 5; i++) {
+			if(write(file, &buf, 1) < 0) {
+				perror("write");
+				return 3;
+			}
+			sleep(1);
+		}
+	}
+	close(file);
+}
diff --git a/Year 3/System programming/Practice05/ex4.c b/Year 3/System programming/Practice05/ex4.c
new file mode 100644
index 0000000..2a77f41
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex4.c
@@ -0,0 +1,36 @@
+#include <unistd.h> // fork, write, read, close, sleep
+#include <fcntl.h> // open
+#include <stdio.h> // perror
+
+int main(int argc, char* argv[]) {
+	int f1 = open(argv[1], O_RDONLY);
+	if (f1 < 0) {
+		perror("open");
+		return 1;
+	}
+
+	int f2 = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC);
+	if (f2 < 0) {
+		perror("open");
+		return 2;
+	}
+
+	pid_t fpid = fork();
+	if (fpid == 0) { // in child
+		char buf = 'c';
+		for (int i = 0; i < 20; i++) {
+			sleep(2);
+			write(f2, &buf, 1);
+		}
+	}
+	else {
+		char buf;
+		while (read(f1, &buf, 1)) {
+			write(f2, &buf, 1);
+			sleep(1);
+		}
+	}
+
+	close(f1);
+	close(f2);
+}
diff --git a/Year 3/System programming/Practice05/ex5.c b/Year 3/System programming/Practice05/ex5.c
new file mode 100644
index 0000000..8e7bf15
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex5.c
@@ -0,0 +1,39 @@
+#include <unistd.h> // fork, write, read, close, sleep
+#include <fcntl.h> // open
+#include <stdio.h> // perror
+#include <sys/wait.h> // waitpid, WNOHANG
+
+int main(int argc, char* argv[]) {
+	int f1 = open(argv[1], O_RDONLY);
+	if (f1 < 0) {
+		perror("open");
+		return 1;
+	}
+
+	int f2 = open(argv[2], O_WRONLY | O_CREAT | O_APPEND);
+	if (f2 < 0) {
+		perror("open");
+		return 2;
+	}
+
+	pid_t fpid = fork();
+	if (fpid == 0) { // in child
+		char buf;
+		while (read(f1, &buf, 1)) {
+			write(f2, &buf, 1);
+			sleep(1);
+		}
+	}
+	else {
+		int status = -2;
+		char buf = 'p';
+		while(status == -2) {
+			sleep(2);
+			write(f2, &buf, 1);
+			waitpid(fpid, &status, WNOHANG);
+		}
+	}
+
+	close(f1);
+	close(f2);
+}
diff --git a/Year 3/System programming/Practice05/ex6.c b/Year 3/System programming/Practice05/ex6.c
new file mode 100644
index 0000000..7e0376d
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex6.c
@@ -0,0 +1,15 @@
+#include <unistd.h> // execvp, fork
+#include <stdio.h> // printf
+#include <sys/wait.h> // wait
+
+int main(int argc, char* argv[]) {
+	pid_t fpid = fork();
+	if (fpid == 0) {
+		execvp(argv[1], argv + 1);
+	}
+	else {
+		int status;
+		wait(&status);
+		printf("%d %d\n", fpid, status);
+	}
+}
diff --git a/Year 3/System programming/Practice05/ex7.c b/Year 3/System programming/Practice05/ex7.c
new file mode 100644
index 0000000..08df367
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex7.c
@@ -0,0 +1,31 @@
+#include <unistd.h> // execvp, fork
+#include <stdio.h> // printf
+#include <sys/wait.h> // wait
+#include <fcntl.h> // open, O_WRONLY
+
+int main(int argc, char* argv[]) {
+	if (argc < 2) return 1;
+
+	pid_t fpid = fork();
+	if (fpid == 0) {
+		int f = open(argv[argc-1], O_WRONLY | O_TRUNC | O_CREAT, 0755);
+		if (f < 0) {
+			perror("open");
+			return 2;
+		}
+		dup2(f, 1);
+		close(f);
+
+		char* args[argc-1];
+		for (int i = 1; i < argc - 1; i++)
+			args[i-1] = argv[i];
+		args[argc-2] = NULL;
+
+		execvp(argv[1], args);
+	}
+	else {
+		int status;
+		wait(&status);
+		printf("%d %d\n", fpid, status);
+	}
+}
diff --git a/Year 3/System programming/Practice05/ex8.c b/Year 3/System programming/Practice05/ex8.c
new file mode 100644
index 0000000..51082bd
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex8.c
@@ -0,0 +1,39 @@
+#include <unistd.h> // execvp, fork
+#include <stdio.h> // printf
+#include <sys/wait.h> // wait
+#include <fcntl.h> // open, O_WRONLY
+
+int main(int argc, char* argv[]) {
+	if (argc < 2) return 1;
+
+	pid_t fpid = fork();
+	if (fpid == 0) {
+		int fi = open(argv[argc-2], O_RDONLY);
+		if (fi < 0) {
+			perror("open");
+			return 2;
+		}
+		dup2(fi, 0);
+		close(fi);
+
+		int fo = open(argv[argc-1], O_WRONLY | O_TRUNC | O_CREAT, 0755);
+		if (fo < 0) {
+			perror("open");
+			return 3;
+		}
+		dup2(fo, 1);
+		close(fo);
+
+		char* args[argc-2];
+		for (int i = 1; i < argc - 2; i++)
+			args[i-1] = argv[i];
+		args[argc-3] = NULL;
+
+		execvp(argv[1], args);
+	}
+	else {
+		int status;
+		wait(&status);
+		printf("%d %d\n", fpid, status);
+	}
+}
diff --git a/Year 3/System programming/Practice05/ex9.c b/Year 3/System programming/Practice05/ex9.c
new file mode 100644
index 0000000..eb50676
--- /dev/null
+++ b/Year 3/System programming/Practice05/ex9.c
@@ -0,0 +1,47 @@
+#include <unistd.h> // execvp, fork
+#include <stdio.h> // printf
+#include <sys/wait.h> // wait
+#include <fcntl.h> // open, O_WRONLY
+
+int main(int argc, char* argv[]) {
+	if (argc < 2) return 1;
+
+	pid_t fpid = fork();
+	if (fpid == 0) {
+		int fi = open(argv[argc-3], O_RDONLY);
+		if (fi < 0) {
+			perror("open");
+			return 2;
+		}
+		dup2(fi, 0);
+		close(fi);
+
+		int fo = open(argv[argc-2], O_WRONLY | O_TRUNC | O_CREAT, 0755);
+		if (fo < 0) {
+			perror("open");
+			return 3;
+		}
+		dup2(fo, 1);
+		close(fo);
+
+		int fe = open(argv[argc-1], O_WRONLY | O_TRUNC | O_CREAT, 0755);
+		if (fe < 0) {
+			perror("open");
+			return 4;
+		}
+		dup2(fe, 2);
+		close(fe);
+
+		char* args[argc-2];
+		for (int i = 1; i < argc - 2; i++)
+			args[i-1] = argv[i];
+		args[argc-3] = NULL;
+
+		execvp(argv[1], args);
+	}
+	else {
+		int status;
+		wait(&status);
+		printf("%d %d\n", fpid, status);
+	}
+}