From 952bee4ac4e4a97d30fc1d681ff0a9e5168fb9c8 Mon Sep 17 00:00:00 2001
From: Syndamia <kamen@syndamia.com>
Date: Sat, 2 Dec 2023 20:19:43 +0200
Subject: [SP/P04] Solved exercises

---
 Year 3/System programming/Practice04/ex1.c | 12 ++++++++++++
 Year 3/System programming/Practice04/ex2.c | 19 +++++++++++++++++++
 Year 3/System programming/Practice04/ex3.c | 16 ++++++++++++++++
 Year 3/System programming/Practice04/ex4.c | 22 ++++++++++++++++++++++
 4 files changed, 69 insertions(+)
 create mode 100644 Year 3/System programming/Practice04/ex1.c
 create mode 100644 Year 3/System programming/Practice04/ex2.c
 create mode 100644 Year 3/System programming/Practice04/ex3.c
 create mode 100644 Year 3/System programming/Practice04/ex4.c

diff --git a/Year 3/System programming/Practice04/ex1.c b/Year 3/System programming/Practice04/ex1.c
new file mode 100644
index 0000000..da92ec6
--- /dev/null
+++ b/Year 3/System programming/Practice04/ex1.c	
@@ -0,0 +1,12 @@
+#include <stdio.h> // printf, perror
+#include <unistd.h> // getpid, getppid, execlp
+#include <sys/types.h> // pid_t
+int main(int argc, char* argv[]) {
+	pid_t pid = getpid();
+	pid_t parent = getppid();
+	printf("%d %d\n", pid, parent);
+	if (execlp("ps", "ps", (char*)NULL) < 0) {
+		perror("execlp");
+		return 1;
+	}
+}
diff --git a/Year 3/System programming/Practice04/ex2.c b/Year 3/System programming/Practice04/ex2.c
new file mode 100644
index 0000000..21f5f0e
--- /dev/null
+++ b/Year 3/System programming/Practice04/ex2.c	
@@ -0,0 +1,19 @@
+#include <sys/wait.h> // wait
+#include <sys/types.h> // pid_t
+#include <stdio.h> // printf
+#include <unistd.h> // getpid, getppid, fork
+
+int main(int argc, char* argv[]) {
+	printf("%d\n", getpid());
+
+	pid_t f = fork();
+	printf("%d %d\n", f, getpid());
+	if (f == 0) { // in child
+		printf("Parent: %d\n", getppid());
+	}
+	else {
+		int status;
+		wait(&status);
+		printf("Child exit status: %d\n", status);
+	}
+}
diff --git a/Year 3/System programming/Practice04/ex3.c b/Year 3/System programming/Practice04/ex3.c
new file mode 100644
index 0000000..dc32819
--- /dev/null
+++ b/Year 3/System programming/Practice04/ex3.c	
@@ -0,0 +1,16 @@
+#include <unistd.h> // fork, execl
+#include <sys/wait.h> // wait
+#include <sys/types.h> // pid_t
+#include <stdio.h> // printf
+
+int main(int argc, char* argv[]) {
+	pid_t f = fork();
+	if (f == 0) { // in child
+		execl(argv[1], argv[1], (char*)NULL);
+	}
+	else {
+		int status;
+		wait(&status);
+		printf("Exit status: %d\n", status);
+	}
+}
diff --git a/Year 3/System programming/Practice04/ex4.c b/Year 3/System programming/Practice04/ex4.c
new file mode 100644
index 0000000..1014f5c
--- /dev/null
+++ b/Year 3/System programming/Practice04/ex4.c	
@@ -0,0 +1,22 @@
+#include <unistd.h> // fork, execlp
+#include <sys/types.h> // pid_t
+#include <sys/wait.h> // wait
+#include <stdio.h> // printf
+
+int main(int argc, char* argv[]) {
+	pid_t fork1 = fork();
+	pid_t fork2 = fork();
+	if (fork1 == 0) { // in child 1
+		execlp(argv[1], argv[1], (char*)NULL);
+	}
+	else if (fork2 == 0) { // in child 2
+		execlp(argv[2], argv[2], (char*)NULL);
+	}
+	else {
+		int firstStatus, secondStatus;
+		pid_t firstPID = wait(&firstStatus);
+		pid_t secondPID = wait(&secondStatus);
+		printf("%s %d\n", argv[1 + (firstPID != fork1)], firstStatus);
+		printf("%s %d\n", argv[1 + (secondPID != fork1)], secondStatus);
+	}
+}
-- 
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