ed is a powerful line text editor for the Linux and Unix-like systems. It was one of the first standard Unix text editor developed in 1969 by Ken Thompson. Much older and legacy Unix like system only shipped with ed for the rescue purpose. There was no vi. So learning ed might be a good idea. A low-level understanding of ed editor helps when one uses a high-level application such as vi or vim. The “Ed Mastery” book teaches you how to use the ed and forgotten art of Unix where the line-oriented paradigm is the only option. The author describe book as, “If you don’t know ed, you’re not a real sysadmin. Forty years after ed’s introduction, author Michael W Lucas has finally unlocked the mysteries of ed for everyone. With Ed Mastery, you too can become a proper Unix sysadmin.”