strcmp failing to compare strings properly - c

Question

I'm having trouble using strcmp in C.
I'm trying to compare a program's arguments using strcmp but even though the strings are the same it doesn't work. Here is the portion of code.
while(strcmp(argv[i], "-e") != 0)
So for i = 11 if I print the value of argv[i] I get
printf("String %s i %d", argv[i],i);
>> String -e i 11
But the while keeps on going. Any ideas why this is happening?
Code:
while(strcmp(argv[i], "-e") != 0 || i != argc)
{
printf("String %s i %d", argv[i],i);
if(!isdigit((unsigned char)*argv[i]) && strcmp(argv[i], "-t") != 0)
{
archivo = fopen(argv[i] , "r");
TOT_IMG = TOT_IMG + 1;
for(t=0;t<NUM_FUNC_TRAZO;t++)
{
for(d=0;d<NUM_FUNC_DIAMETRICA;d++)
{
for(c=0;c<NUM_FUNC_CIRCO;c++)
{
if (fscanf(archivo, "%s",el) != EOF)
{
par->vector_circo[t][d][c] = strtod(el,NULL);
par->clase = clase;
}
else
{
break;
}
}
}
}
par_temp = par;
par->siguiente = (parametros_lista) malloc(sizeof(parametros_elem));
par = par->siguiente;
par->anterior = par_temp;
}
else
{
if(strcmp(argv[i], "-t") != 0)
{
clase = atoi(argv[i]);
CLASES = CLASES + 1;
}
}
i = i + 1;
}

Answer 1

Let's look at this:
while(strcmp(argv[i], "-e") != 0 || i != argc)
OK, so let's assume strcmp correctly returns 0 when argv[i] is "e". We'll assume this because it's exceedingly unlikely that there's a bug in your library implementation of strcmp.
What happens if strcmp returns 0? Well, things don't just stop, your code checks whether i != argc is true. Is it? My psychic debugging skills tell me that you should look into that second part of the while.
You may also want to note that it's possible that your code could, potentially, access argv[argc], which is NULL. You may get lucky if strcmp is lenient when the input is NULL, but it's a bug that you should fix.

Answer 2

I'd rather recommend you to use getopt (3). This is widely used approach to parameters parsing conforming with POSIX.
Also there was another question related to achieving getopt.h interface on windows: getopt.h: Compiling UNIX C-Code in Windows. What's important it is answered (Xgetopt) so portability should be not a case.