1 files changed, 26 insertions, 0 deletions
diff --git a/rot.c b/rot.c
new file mode 100644
index 0000000..a147376
--- /dev/null
+++ b/rot.c
@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <stdlib.h>
+
+#define mod(A) ((A)%26)
+
+int main(int argc, char **argv)
+{
+    if(argc!=3)
+        exit(1);
+    char *string = *(argv+1);
+    int i, rot = (int)strtol(*(argv+2), NULL, 10);
+    for(i=0; i<strlen(string); i++)
+        if(isalpha(string[i])){
+            if(string[i]-'A'<26){ // Simple way to differentiate lower and upper case if all letters are known to be alpha.
+                putchar(mod(string[i]-'A'+rot)+'A');
+            }else{
+                putchar(mod(string[i]-'a'+rot)+'a');
+            }
+        }else{
+            putchar(string[i]);
+        }
+    putchar('\n');
+    return 0;
+}