How to test permissions of current working directory

[SagaciousKJB]

How can I use stat() to test if the current working directory has proper write permissions? I tried using some of the example code from the manual page but it didn't work as expected.


switch (sb.st_mode & S_IFMT) {
case S_IFBLK: printf("block device\n"); break;
case S_IFCHR: printf("character device\n"); break;
case S_IFDIR: printf("directory\n"); break;
case S_IFIFO: printf("FIFO/pipe\n"); break;
case S_IFLNK: printf("symlink\n"); break;
case S_IFREG: printf("regular file\n"); break;
case S_IFSOCK: printf("socket\n"); break;
default: printf("unknown?\n"); break;
}


They use this switch to print what type of file it is. Couldn't I make a similar switch with st_mode and the S_IRWXU to test which permissions the user has in the folder? So like...


switch (sb.st_mode & S_IRWXU) {
case S_IWUSR: printf("Owner has write permission\n"); break;
.....................................
}


The problem is the switch loop doesn't seem to read the S_IWUSR flag and will just go to the default option. Haven't tired it with group or other permissions yet, seems like I'm doing something wrong.

[ofnuts]

That doesn't work because unlike Dir/Link/File types, the authorisations can happen together. So sb.st_mode & S_IRWXU==S_IWUSR is true only if the user has write access and nothing else (no read, no execute). To test for your own read access you just need to test sb.st_mode&S_IWUSR != 0.

[SagaciousKJB]

That doesn't work because unlike Dir/Link/File types, the authorisations can happen together. So sb.st_mode & S_IRWXU==S_IWUSR is true only if the user has write access and nothing else (no read, no execute). To test for your own read access you just need to test sb.st_mode&S_IWUSR != 0.

So if I did if(sb.st_modes&S_IWUSR != 0) is that true if I do have permissions or don't?

[ofnuts]

My money on the fact that you have the permission. But easy to test...

[SagaciousKJB]

My money on the fact that you have the permission. But easy to test...

Eh I'm sorry, I don't understand

[ofnuts]

I don't know, it is a lot more likely that a bit set indicates that access is granted. You can check the doc or experiment (see how the flag value changes when you do a chmod on the file).

[SagaciousKJB]

I don't know, it is a lot more likely that a bit set indicates that access is granted. You can check the doc or experiment (see how the flag value changes when you do a chmod on the file).

Yeah, the manual wasn't making too much sense of it for me. Think I'm gonna try that experimenting idea.