Question

5. PracticalC Programming a. (4 Points) Why should we use snprintf () instead of sprintf(), strncpy () instead of strcpy (), etc.? Seriously, how bad can using sprintf(), strcpy ), etc. be? b. (4 Points) What does extern mean? What does it tell the compiler to do? c. (8 Points) The program below will compile well but run poorly. Please make it do error checking and fix it to make it proper: #include #include <stdlib.h> <stdio.h> <sys/types.h> <sys/stat.h> #include #include #include <fcntl.h> =256 const int LINE LEN main int (int argc, char* argv open (argv[1,0_RDONLY, 0660); open (argv[2] ,0_RDONLY, 0660) ; int fdIn0 int fdInl char* line0; char* linel; numBytes0; numBytes1 =0; int int int count ( ( (numBytes0 = read (fdIn0, line0, LINE_LEN)) > 0) (numBytes1 = read (fdInl, linel , LINE_LEN)) > 0) while && numBytes < numBytes1) ? numBytes0 numBytes1; int numBytes int i (i = 0; i < numBytes; for i++) if (line0[i] != line1[i]. count++ }

$printf(%d\n, count); return (EXIT_SUCCESS);$

Answer 1

a)

snprintf() and sprintf() will give the same result.

snprintf is more generic than sprintf and it will protect the string from the overruns no matter the given format of string.

Because snprintf adds a final \0 , you should make the string buffer one byte bigger than sprintf

b)

An external variable is a variable defined outside any function block

The 'extern' keyword means "declare without defining".

An external variable may also be declared inside a function.

Each time, it must be declared every time it is to be used

It tells the compiler that it is like a global variable which will be initialized to zero(0) initially

When this variable is declared inside a function, the 'extern' keyword is important because if not specified, the compiler will assume it as a local variable .

To differentiate from local variable , the 'extern' keyword is needed

c)

There is an errror called  ""invalid suffix "_RDONLY" on integer constant""

So the program does not work properly

if you dont use it you will be able to run the program without any errors