how to copy binary files in c - c

Question

hello guys i am trying to make a program which which copying binary files (the values) from the source to the target. but i has a mistake and i don't know how to solve that, how can i complete the code?
int main(int argc, char ** argv)
{
FILE * source, *target;
int numr, numw;
char buffer[100];
source = fopen(argv[1], "rb");
target = fopen(argv[2], "rb");
if ((source = fopen(argv[1], "rb")) == NULL)
{
printf("open read file error.\n");
return 0;
}
while (feof(source) == 0)
{
if ((numr = fread(buffer, 1, 100, source)) != 100)
{
if (ferror(target) != 0)
{
printf("read file error.\n");
return 0;
}
}
fwrite(buffer, 1, numr, target);
if ((numw = fwrite(buffer, 1, numr, target)) != numr)
{
printf("write file error.\n");
return 0;
}
}
fclose(source);
fclose(target);
return 0;
}

Answer 1

At first, you wont open source file twice. Just remove first or second fopen from code.
source = fopen(argv[1], "rb");
if (source == NULL)
{
printf("open read file error.\n");
return 0;
}
Also must open target file with "w" and check it for success.
target = fopen(argv[2], "a+w");
if (target == NULL)
{
fclose(source);
printf("open target file error.\n");
return 0;
}
Also you dont need to check that fread returned 100, if there is something wrong, ferror() will detect error for you.
numr = fread(buffer, 1, 100, source);
if (ferror(target) != 0)
{
printf("read file error.\n");
break;
}
Also you must use write function once
numw = fwrite(buffer, sizeof(char), numr, target);
if (numw != numr)
{
printf("write file error.\n");
break;
}
I edited your code and now it works fine...
int main(int argc, char ** argv)
{
FILE *source, *target;
int numr, numw;
char buffer[101];
source = fopen(argv[1], "rb");
if (source == NULL)
{
printf("open read file error.\n");
return 0;
}
target = fopen(argv[2], "a+w");
if (target == NULL)
{
fclose(source);
printf("open target file error.\n");
return 0;
}
while (feof(source) == 0)
{
memset(buffer, 0, sizeof(buffer));
numr = fread(buffer, 1, 100, source);
if (ferror(target) != 0)
{
printf("read file error.\n");
break;
}
numw = fwrite(buffer, sizeof(char), numr, target);
if (numw != numr)
{
printf("write file error.\n");
break;
}
}
fclose(source);
fclose(target);
return 0;
}