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cposixmkdirumask

How to create directory with right permissions using C on Posix

I am trying to write a simple C program that creates directories (a mkdir clone.). This is what I have so far:

#include <stdlib.h>
#include <sys/stat.h> // mkdir
#include <stdio.h> // perror

mode_t getumask()
{
    mode_t mask = umask(0);
    umask (mask);
    return mask;
}

int main(int argc, const char *argv[])
{
    mode_t mask = getumask();
    printf("%i",mask);

    if (mkdir("trial",mask) == -1) {
        perror(argv[0]);
        exit(EXIT_FAILURE);
    }
    return 0;
}

This code creates directory with d--------- but I want it to create it with drwxr-xr-x like mkdir do? What am I doing wrong here?

Solution

  • As Eric says, umask is the complement of the actual permission mode you get. So instead of passing mask itself to mkdir(), you should pass 0777-mask to mkdir().