init commit

3sem/seminars/l3/02.c

@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/file.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+int
+main(int argc, char *argv[])
+{
+    int fdin = open("in", O_RDWR);
+    if (fdin == -1) {
+        return 1;
+    }
+
+    double num1, num2;
+
+    // Read the first double
+    if (read(fdin, &num1, sizeof(double)) != sizeof(double)) {
+        close(fdin);
+        return 1;
+    }
+
+    // Read the second double
+    if (read(fdin, &num2, sizeof(double)) != sizeof(double)) {
+        close(fdin);
+        return 1;
+    }
+
+    // Move the file pointer back to the beginning
+    if (lseek(fdin, 0, SEEK_SET) == -1) {
+        close(fdin);
+        return 1;
+    }
+
+    // Write the second double first
+    if (write(fdin, &num2, sizeof(double)) != sizeof(double)) {
+        close(fdin);
+        return 1;
+    }
+
+    // Write the first double second
+    if (write(fdin, &num1, sizeof(double)) != sizeof(double)) {
+        close(fdin);
+        return 1;
+    }
+
+    close(fdin);
+
+    return 0;
+}