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

I'm not sure you can fseek/ftell pipe streams like this.

Have you checked the value of bufSize ? One reason malloc be failing is for insanely sized buffers.

Answer 2

To answer the question in the update:

char buffer[1024];
char * line = NULL;
while ((line = fgets(buffer, sizeof buffer, fp)) != NULL) {
    // parse one line of df's output here.
}

Would this be enough?

Answer 3

First thing to check is the value of bufSize - if that happens to be <= 0, chances are that malloc returns a NULL as you're trying to allocate a buffer of size 0 at that point.

Another workaround would be to ask malloc to provide you with a buffer of the size (bufSize + n) with n >= 1, which should work around this particular problem.

That aside, the code you posted is pure C, not C++, so including is overdoing it a little.