tasks a-s

Task/Copy-a-string/C/copy-a-string-1.c

@@ -0,0 +1,60 @@
+#include <stdlib.h>	/* exit(), free() */
+#include <stdio.h>	/* fputs(), perror(), printf() */
+#include <string.h>
+
+int
+main()
+{
+	size_t len;
+	char src[] = "Hello";
+	char dst1[80], dst2[80];
+	char *dst3, *ref;
+
+	/*
+	 * Option 1. Use strcpy() from <string.h>.
+	 *
+	 * DANGER! strcpy() can overflow the destination buffer.
+	 * strcpy() is only safe if the source string is shorter than
+	 * the destination buffer. We know that "Hello" (6 characters
+	 * with the final '\0') easily fits in dst1 (80 characters).
+	 */
+	strcpy(dst1, src);
+
+	/*
+	 * Option 2. Use strlen() and memcpy() from <string.h>, to copy
+	 * strlen(src) + 1 bytes including the final '\0'.
+	 */
+	len = strlen(src);
+	if (len >= sizeof dst2) {
+		fputs("The buffer is too small!\n", stderr);
+		exit(1);
+	}
+	memcpy(dst2, src, len + 1);
+
+	/*
+	 * Option 3. Use strdup() from <string.h>, to allocate a copy.
+	 */
+	dst3 = strdup(src);
+	if (dst3 == NULL) {
+		/* Failed to allocate memory! */
+		perror("strdup");
+		exit(1);
+	}
+
+	/* Create another reference to the source string. */
+	ref = src;
+
+	/* Modify the source string, not its copies. */
+	memset(src, '-', 5);
+
+	printf(" src: %s\n", src);   /*  src: ----- */
+	printf("dst1: %s\n", dst1);  /* dst1: Hello */
+	printf("dst2: %s\n", dst2);  /* dst2: Hello */
+	printf("dst3: %s\n", dst3);  /* dst3: Hello */
+	printf(" ref: %s\n", ref);   /*  ref: ----- */
+
+	/* Free memory from strdup(). */
+	free(dst3);
+
+	return 0;
+}

Task/Copy-a-string/C/copy-a-string-2.c

@@ -0,0 +1,22 @@
+#include <stdlib.h>	/* exit() */
+#include <stdio.h>	/* fputs(), printf() */
+#include <string.h>
+
+int
+main()
+{
+	char src[] = "Hello";
+	char dst[80];
+
+	/* Use strlcpy() from <string.h>. */
+	if (strlcpy(dst, src, sizeof dst) >= sizeof dst) {
+		fputs("The buffer is too small!\n", stderr);
+		exit(1);
+	}
+
+	memset(src, '-', 5);
+	printf("src: %s\n", src);  /* src: ----- */
+	printf("dst: %s\n", dst);  /* dst: Hello */
+
+	return 0;
+}