Get the file sizes of multiple files from stdin (C) - c

Question

I am trying to read and get the total of filesizes of multiple files from 1 line from stdin. The code below works perfectly if there is 1 file but if there are multiple it fails because it cannot distinguish when 1 file ends and the other begins. The filenames are separated by whitespace (ex: echo "file1.txt file2.txt"), can someone point me in the right direction to how I can evaluate each filename's size individually? The filesize function was not included for the sake of brevity
int main (int argc, char *argv[])
{
char tmpstring[1024];
const char* fileName;
off_t size;
char* pos;
int total = 0;
//read from stdin
while (fgets(tmpstring, 1024, stdin))
{
fileName = tmpstring;
if ((pos=strchr(fileName, '\n')) != NULL)
*pos = '\0';
printf("this is the name: %s\n", fileName); //#DEBUG
size = filesize(fileName);
total += size;
//} #DEBUG
}
printf("This is the total: %d\n", total); //#DEBUG
return -1;
}

Answer 1

How about using scanf instead:
int main() {
char buffer[1024];
int total = 0;
while (scanf("%1023s", buffer) == 1) {
printf("this is the name: %s\n", buffer);
total += filesize(buffer);
}
printf("This is the total: %d\n", total);
return 0; // You shouldn't return -1!
}
scanf first consumes leading whitespace, and then reads a sequence of non-whitespace characters. The return value 1 indicates that a string was successfully read (caveat: scanf actually returns the number of input items matched; see the manual!).
The maximum field width specifier (the 1023 in %1023s) is necessary to avoid a buffer overflow vulnerability. Had I omitted it, it would have been possible to feed a string much longer than 1023 characters to scanf. The extra character is required to store the null terminator.
Note: A (possibly undesirable) side-effect of this approach is that it's not necessary to enter all the file names on a single line. If you don't want this behavior, a modification of your initial approach does the trick:
int main(int argc, char *argv[]) {
char buffer[1024];
const char* fileName;
int total = 0;
char *pos;
// Read from stdin. You should do some error checking too.
fgets(buffer, sizeof buffer, stdin);
// Get rid of the trailing '\n'.
if ((pos = strchr(buffer, '\n')) != NULL)
*pos = '\0';
fileName = strtok(buffer, " ");
while (fileName) {
printf("this is the name: %s\n", fileName);
total += filesize(fileName);
fileName = strtok(NULL, " ");
}
printf("This is the total: %d\n", total);
return 0;
}
On a side note, you shouldn't be using int to represent file sizes. It is quite likely that int is only 32 bits on your machine, in which case even a few relatively small files could overflow it.