/in/foo.c: In function 'main':
/in/foo.c:7:10: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char (*)[100]' [-Wformat=]
  scanf("%s",&str);
          ^
/in/foo.c:8:4: warning: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
  n=strlen(str);
    ^~~~~~
/in/foo.c:8:4: warning: incompatible implicit declaration of built-in function 'strlen'
/in/foo.c:8:4: note: include '<string.h>' or provide a declaration of 'strlen'