Bug/Gross InEfficiency in HeathField's fgetline program

The function below is from Richard HeathField's fgetline program. For
some reason, it makes three passes through the string (a strlen(), a
strcpy() then another pass to change dots) when two would clearly be
sufficient. This could lead to unnecessarily bad performance on very
long strings. It is also written in a hard-to-read and clunky style.

char *dot_to_underscore(const char *s)
{
char *t = malloc(strlen(s) + 1);
if(t != NULL)
{
char *u;
strcpy(t, s);
u = t;
while(*u)
{
if(*u == '.')
{
*u = '_';
}
++u;
}
}
return
t;
}

Proposed solution:

char *dot_to_underscore(const char *s)
{
char *t, *u;
if(t=u=malloc(strlen(s)+1))
while(*u++=(*s=='.' ? s++, '_' : *s++));
return t;
}

.

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