How do I read the results of a system() call in C++?

Question

I\'m using the following code to try to read the results of a df command in Linux using popen.

#include  // file an         


        

Answer 1

Why would std::malloc() fail?

The obvious reason is "because std::ftell() returned a negative signed number, which was then treated as a huge unsigned number".

According to the documentation, std::ftell() returns -1 on failure. One obvious reason it would fail is that you cannot seek in a pipe or FIFO.

There is no escape; you cannot know the length of the command output without reading it, and you can only read it once. You have to read it in chunks, either growing your buffer as needed or parsing on the fly.

But, of course, you can simply avoid the whole issue by directly using the system call df probably uses to get its information: statvfs().