A collection of Ideas from 15

• 15.3 discusses changing file ownership
  • When a file is created, the owner is set to the effective id of the creating process.

  •        #include <unistd.h>
    
           int chown(const char *pathname, uid_t owner, gid_t group);
           int fchown(int fd, uid_t owner, gid_t group);
           int lchown(const char *pathname, uid_t owner, gid_t group);
    	 

  • As you would expect for arguments.
  • Only privileged process can do this.
  • Setuid bit and setgid bit is cleared.
  • lchonw changes the ownership of a symbolic link.
  • -1 on error.
  • See the system chown command.
• 15.4 discusses file permissions, but we have done that.

  •        #include <sys/stat.h>
    
           int chmod(const char *pathname, mode_t mode);
           int fchmod(int fd, mode_t mode);
    	 

    • Changes file permissions.
    • Only if you are allowed

  •  
     #include <unistd.h>
     int access(const char *pathname, int mode);
              

    • Mode, can be |
      • F_OK: does the file exist
      • R_OK: does the proces have read permission
      • W_OK: does the process have write permissions
      • X_OK: does the process have execute permission
    • Due to multiprocessing, results can change after call.
• Chapter 15 also deals with time stamps, but we have yet to deal with time.