Shell Scripting: Expert Recipes for Linux, Bash, and More

The Bourne Again Shell

Bash is the standard interactive shell on most GNU/Linux and Mac OSX systems, and is becoming popular with traditional Unix users, too. It is also the default shell for the Cygwin environment, which provides GNU tools under Microsoft Windows. It is compatible with the Bourne shell, but adds a number of extra features, most of which are covered in this book. The name of the bash shell (the “Bourne Again shell”) is a play on the name of the author of the Bourne shell.

Bash was initially written by Brian Fox in 1988 for the Free Software Foundation (FSF) and is currently maintained by Chet Ramey. It takes some ideas from various shells including csh and ksh. Most noticeably, bash uses [[ … ]], $( … ), and (( … )) syntaxes from ksh.

Bash, if called as sh, acts more like the Bourne shell in the configuration files it reads. This is documented in more detail later in this chapter.