c - Query regarding main() of GRUB -

below code of main() of grub. here want know line:

file = fopen(arg_v[1], "rb");

here file fopen opening? file arg v[1] pointing to?

int main(unsigned arg_c, char *arg_v[])     {         file *file;          if(arg_c < 2)         {             printf("checks if file multiboot compatible\n");             return 1;         }         file = fopen(arg_v[1], "rb");         if(file == null)         {             printf("can't open file '%s'\n", arg_v[1]);             return 2;         }         check_multiboot(arg_v[1], file);         fclose(file);         return 0;     } 

if call program with

program arg1 arg2.txt 65

argv[1] pointer "arg1"; argv[2] pointer "arg2.txt", argv[3] pointer "65", argv[4] null

argv[0] either points "program" or "" if os and/or library and/or startup code cannot identify name used call binary executable

in specific case, program tries open file, name provided in first argument program, in read binary mode.