Question

With Bash you can do a simple variable test like this

$ [ $foo ]; echo $?
1

$ foo=bar

$ [ $foo ]; echo $?
0

The expression is true if and only if the argument is not null.

What would be a similar test with C?

Edit

Lets say an int type for argument sake.

Answer 1

In general, there is implicit boolean conversion in C. So all of the following will print “bad”:

int a = 0;
if (a) {                  // if a is nonzero.
    printf("good");
}
else {
    printf("bad");
}

char* str = NULL;
if (str) {                  // if str is nonzero. (NULL is zero).
    printf("good");
}
else {
    printf("bad");
}