Section 2.4. Linux Shells

2.4. Linux Shells

Build environments may also use shell scripts to kick off tasks and procedures when building the application. Linux provides support for the most commonly used shells from other UNIX platforms. Depending on the Linux installation, several shells developed for Linux are installed by default. The more popular shells developed for Linux are as follows:

• bash. A shell or command language interpreter that is an sh-compatible shell incorporating features from the Korn shell (ksh) and C shell (csh). It is intended to conform to the IEEE POSIX P1003.2/ISO 9945.2 Shell and Tools standard. Most sh scripts can be run with bash without modification. Refer to www.gnu.org/software/bash/bash.html for more information. bash is the default shell on almost all Linux distributions.

• tcsh. A shell or command language interpreter that is a completely compatible version of the Berkeley UNIX C shell (csh). It can be used as an interactive login shell and a shell script command processor. For more detailed information about csh, refer to www.tcsh.org.

• zsh. A shell or command language interpreter that incorporates many of the useful features of bash, ksh, and tcsh as well as its own original features. To get more information about zsh, refer to http://zsh.sourceforge.net/.

• pdksh. A shell or command language interpreter that is a clone of the AT&T Korn shell. It has most of the ksh88 features as well as some ksh93 features. For more information about pdksh, refer to http://web.cs.mun.ca/~michael/pdksh/.

An excellent reference book about UNIX and Linux shells that can be helpful during the porting process is UNIX Shells by Example, 4th Edition, by E. Quigley (Prentice Hall, 2005).