man pages section 2: System Calls
    
U
 
 ulimit - get and set process limits ( Index Term Link )
 
 umask - set and get file creation mask ( Index Term Link )
 
 umount - unmount a file system ( Index Term Link )
 
 umount2 - unmount a file system ( Index Term Link )
 
 uname - get name of current operating system ( Index Term Link )
 
 unlink - remove directory entry ( Index Term Link )
 
 unmount a file system - umount2 ( Index Term Link )
 
 unmount a file system - umount ( Index Term Link )
 
 user audit identity
  get user audit identity - getauid ( Index Term Link )
  set user audit identity - setauid ( Index Term Link )
 
 user ID, set real and effective - setreuid() ( Index Term Link )
 
 user IDs
  get - getuid, geteuid ( Index Term Link )
  set - setuid ( Index Term Link )
 
 utime - set file access and modification times ( Index Term Link )
 
 utimes - set file access and modification times ( Index Term Link )