Question

I am doing “cat words | sign” (words is the text file and sign is the c program). However this seems to generate a infinite loop. Any idea how to solve this?

And what is the meaning of

sign < words | @sort > out

Below is the code for the c program.

int main(){
    char words[80];
    scanf("%s", words);
    printf(words);
    string_sort(words);
    printf(" ");
    printf(words);
    printf("\n");

    while ( words != ""){
            scanf("%s", words);
            printf("%s", words);
            string_sort(words);
            printf("%s", " ");
            printf("%s", words);
            printf("\n");
    }
 }

Answer 1

When the program reaches EOF, scanf() leaves words unchanged, wich causes words != "" always be true.

Instead of testing words, you should test for feof(stdin).