将stdout和stderr重定向到文件中

Question

I want to redirect the output of a system call into a file .. I tried this..

#include <stdio.h>
int main()
{
        system("ls >> temp.txt");
        return 0;
}

But this is only working for system calls .. If i put some other thing in place of ls , the error output is not redirected into the file.. it is just printed on the console ..

For example

#include <stdio.h>
int main()
{
system("hello >> temp.txt");
return 0;
}

I want the error output redirected to the file.. how can i do this? thanks..

Answer 1

it can be achieved by

system("hello > temp.txt 2>&1");

This will direct both standard output and standard error to the file temp.txt..

while

system("hello 2>&1 > temp.txt");

This will only direct standard output to temp.txt..

NOTE:

The greater-than sign should not be separated by spaces from the number of the file descriptor. If it would be separated, we would be pointing the output to a file again.