/in/ex1.c: In function 'main':
/in/ex1.c:8:14: error: conversion to 'int' from 'size_t {aka long unsigned int}' may alter its value [-Werror=conversion]
     int len= strlen(arr);
              ^~~~~~
/in/ex1.c:12:18: error: conversion to 'char' from 'int' may alter its value [-Werror=conversion]
         {arr[i]= toupper(arr[i])}
                  ^~~~~~~
/in/ex1.c:12:33: error: expected ';' before '}' token
         {arr[i]= toupper(arr[i])}
                                 ^
/in/ex1.c:14:10: error: variable 'file' set but not used [-Werror=unused-but-set-variable]
     char file[600][30];
          ^~~~
cc1: all warnings being treated as errors