如何使用fcntl.h以附加模式写入文件

Question

Below is my code:

#include <iostream> 
#include <fcntl.h>
#include <unistd.h>
using namespace std; 

int main()
{

int filedesc = open("testfile.txt", O_RDWR | (O_APPEND |O_CREAT) ,S_IRWXO);

    if (filedesc < 0) {
    cout<<"unable to open file";
        return -1;
    }

    if (write(filedesc, "This will be output to testfile.txt", 36) != -1) {
        cout<<"writing";
        close( filedesc );
    }

    return 0;
return 0;

}

If i run same above second time the o/p is "unable to open file". Am i doing something wrong?

Answer 1

This is a permission issue

Try changing

S_IRWXO 

to

 S_IRWXU

It will work fine

S_IRWXO

read, write, execute/search by others

Reference http://pubs.opengroup.org/onlinepubs/7908799/xsh/sysstat.h.html