How can I determine if a file is read-only for my process on *nix? [duplicate]

Answer 1

Something like this:

if ( access( filename, W_OK )) { /* writable */ }

See access(2).

Answer 2

You don't want to use stat() for this. You want to use access() from <unistd.h>:

char const* name = "file";
if (access(name, R_OK)) {
    std::cout << "'" << name << "' is readable\n";
}
if (access(name, W_OK)) {
    std::cout << "'" << name << "' is writable\n";
}

Answer 3

Use getuid()/geteuid() to determine the process's user ID, and similarly getgid()/getegid() for the group ID. Then you can compare to the owner/group of the file (which you get from stat or lstat) and cross-reference the permission bits.