Extend the test to include checks on truncate.

programs/tests/t_write_read.c

@@ -11,48 +11,115 @@
 #include <sys/stat.h>
 #include <sys/unistd.h>
 
-int main(int argc, char *argv[])
+int test_write_read()
 {
-    char *file = "t_write_read_file";
+    char *filename  = "t_write_read_file";
     mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP;
 
-    int fd = creat(file, mode);
+    int fd = creat(filename, mode);
     if (fd < 0) {
-        printf("Failed to open file %s: %s\n", file, strerror(errno));
-        exit(EXIT_FAILURE);
+        printf("Failed to open file %s: %s\n", filename, strerror(errno));
+        return 1;
     }
 
     if (write(fd, "foo", 3) != 3) {
-        printf("First write to %s failed: %s\n", file, strerror(errno));
-        exit(1);
+        printf("First write to %s failed: %s\n", filename, strerror(errno));
+        return 1;
     }
 
     if (write(fd, "bar", 3) != 3) {
-        printf("Second write to %s failed: %s\n", file, strerror(errno));
-        exit(1);
+        printf("Second write to %s failed: %s\n", filename, strerror(errno));
+        return 1;
     }
 
     close(fd);
 
-    fd = open(file, O_RDONLY, 0);
+    fd = open(filename, O_RDONLY, 0);
     if (fd < 0) {
-        printf("Failed to open file %s: %s\n", file, strerror(errno));
-        exit(1);
+        printf("Failed to open file %s: %s\n", filename, strerror(errno));
+        return 1;
     }
 
     ssize_t bytes_read;
     char buf[7];
     buf[6] = 0;
     if ((bytes_read = read(fd, &buf, 6)) < 0) {
-        printf("Reading from file %s failed: %s\n", file, strerror(errno));
-        exit(1);
+        printf("Reading from file %s failed: %s\n", filename, strerror(errno));
+        return 1;
     }
+    close(fd);
 
     if (strcmp(buf, "foobar") != 0) {
         printf("Unexpected file content: %s\n", buf);
-        exit(1);
+        return 1;
+    }
+
+    unlink(filename);
+    return 0;
+}
+
+int test_truncate()
+{
+    char *filename = "test.txt";
+    mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP;
+    char buffer[7];
+    ssize_t bytes_read;
+    int fd;
+
+    // Create the file.
+    fd = creat(filename, mode);
+    if (fd < 0) {
+        printf("Failed to open file %s: %s\n", filename, strerror(errno));
+        return 1;
+    }
+    if (write(fd, "foobar", 6) != 6) {
+        printf("First write to %s failed: %s\n", filename, strerror(errno));
+        return 1;
+    }
+    close(fd);
+
+    // Override the content.
+    fd = open(filename, O_RDWR | O_TRUNC, 0);
+    if (fd < 0) {
+        printf("Failed to open file %s: %s\n", filename, strerror(errno));
+        return 1;
+    }
+    if (write(fd, "bar", 3) != 3) {
+        printf("Overriding the content of %s failed: %s\n", filename, strerror(errno));
+        return 1;
     }
+    // Go back to the beginning.
+    lseek(fd, 0, SEEK_SET);
+    // Read the content.
+    if ((bytes_read = read(fd, &buffer, 6)) < 0) {
+        printf("Reading from file %s failed: %s\n", filename, strerror(errno));
+        return 1;
+    }
+    // Close the file.
+    close(fd);
 
-    unlink(file);
+    printf("We found `%s`\n", buffer);
+
+    if (strcmp(buffer, "bar") != 0) {
+        printf("Unexpected file content: %s\n", buffer);
+        return 1;
+    }
+
+    // Delete the file.
+    unlink(filename);
     return 0;
 }
+
+int main(int argc, char *argv[])
+{
+    printf("Running `test_write_read`...\n");
+    if (test_write_read()) {
+        exit(EXIT_FAILURE);
+    }
+    printf("Running `test_truncate`...\n");
+    if (test_truncate()) {
+        exit(EXIT_FAILURE);
+    }
+
+    return EXIT_SUCCESS;
+}