Question

I’m working on a homework assignment and I ran into a little snag.

I’m trying to read a filename from standard input and then stat the file to get the size (as per the assignment’s requirements):

#define BUFFSIZE 4096

int
main(void) {
    int n;

    char buffer[BUFFSIZE];

    struct stat buf;

    while ((n = read(STDIN_FILENO, buffer, BUFFSIZE)) > 0) {
        stat(buffer, &buf);
        perror("stat");
    }
}

Here’s the output when ran (I entered the filename file):

file
stat: No such file or directory

But if I try something like this:

#define BUFFSIZE 4096

int
main(void) {
    int n;

    char buffer[BUFFSIZE] = "file";

    struct stat buf;

    stat(buffer, &buf);
    perror("stat");
}

I get:

stat: Success

The file named file is in the directory that I’m running the program from.

How come there is a difference between reading in the string “file” and just initializing the array to the string “file”?

Answer 1

Before calling stat() print the value of buffer to standard output:

printf("[%s]\n", buffer);

It will not be what you expect as read() will not NULL terminate buffer for you.
Initialise buffer before read().

Not sure why you looping on the read() as you should acquire the complete name of the file before calling stat(). If you have not been forced to use read() consider using fgets().