Question

My professor cited this example in class. Its basically a version of the Unix more command, and I’m unsure about a couple things in it

int main( int ac , char *av[] )
{
  FILE  *fp;

  if ( ac == 1 )
    do_more( stdin );
  else
    while ( --ac )
     if ( (fp = fopen( *++av , "r" )) != NULL )
     {
        do_more( fp ) ; 
        fclose( fp );
     }
     else
        exit(1);
return 0;
}

I understand that *fp defines a file pointer, and that *av[] is the array of command line arguments. But what does *++av mean in terms of operation?

Answer 1

read *++av like this:

++av // increment the pointer
*av // get the value at the pointer, which will be a char*

in this example, it will open every files passed on the command line.

also:

av[0] // program name
av[1] // parameter 1
av[2] // parameter 2
av[3] // parameter 3
av[ac - 1] // last parameter