Why do I get an empty newline with fgets()

Question

    argv0 = "delreves";

    int m;
    for(m = 1;m < argc;m++){
        char buffer[256];       
        FILE *fd;
        fd = fopen(argv[m],"r"); 
        if(fd==NULL){
            Error (EX_NOINPUT, "%s", "Fallo");
        }   
        while(fgets(buffer,256,fd)){
            int size = strlen(buffer);

            int l=size-1;
            int j;              
            for(j = 0; j < size/2; j++, l--){
                        char temp = buffer[j];
                    buffer[j] = buffer[l];
                    buffer[l] = temp;
            }
        printf("%s",buffer);            
        }

    fclose(fd);

    }

}

After running the program with a days of week file I have

./a.out file.txt

yadnom
yadseut
....

---

How can I eliminate the empty newline before the first day?

Answer 1

The function fgets is returning the string ending with the newline character, if encountered in the input file. Your algorithm is reversing the string, preserving the newline, so it is coming as a first character of the output. An this is what you see: newline and then the string. If you want to eliminate it, just discard the last character of the input (replace it with \\0 ), or work with length-1.