File read using POSIX API's

Question

Consider the following piece of code for reading the contents of the file into a buffer

#include 
#include 
#include 

        

Answer 1

You could consider allocating the buffer dynamically by first creating a buffer of a fixed size using malloc and doubling (with realloc) the size when you fill it up. This would have a good time complexity and space trade off.

At the moment you repeatedly read into the same buffer. You should increase the point in the buffer after each read otherwise you will overwrite the buffer contents with the next section of the file.

The code you supply allocates 50 bytes for the buffer yet you pass 4096 as the size to the read. This could result in a buffer overflow for any files over the size of 50 bytes.

As for the `\n' and '\0'. The newline is probably in the file and the '\0' was just already in the buffer. The buffer is allocated on the stack in your code and if that section of the stack had not been used yet it would probably contain zeros, placed there by the operating system when your program was loaded.

The operating system makes no attempt to terminate the data read from the file, it might be binary data or in a character set that it doesn't understand. Terminating the string, if needed, is up to you.

A few other points that are more a matter of style:

• You could consider using a for (i = 0; buff[i]; ++i) loop instead of a while for the printing out at the end. This way if anyone messes with the index variable i you will be unaffected.
• You could close the file earlier, after you finish reading from it, to avoid having the file open for an extended period of time (and maybe forgetting to close it if some kind of error happens).