The following sections introduce several of the most common shells available with Linux.
Using bash (and Earlier sh) Shells
As mentioned earlier, the name bash is an acronym for Bourne Again Shell, acknowledging the
roots of bash coming from the Bourne shell (sh command) created by Steve Bourne at AT&T Bell
Labs. Brian Fox of the Free Software Foundation created bash, under the auspices of the GNU
Project. Development was later taken over by Chet Ramey at Case Western Reserve University.
Bash includes features originally developed for sh and ksh shells in early UNIX systems, as well as
some csh features. Expect bash to be the default shell in whatever Linux system you are using, with
the exception of some specialized Linux systems (such as those run on embedded devices or run
from a floppy disk) that may require a smaller shell that needs less memory and entails fewer features.
Most of the examples in this chapter are based on the bash shell.
The bash shell is worth knowing not only because it is the default in most installations,
but because it is the one tested in most Linux certification exams.
Bash can be run in various compatibility modes so that it behaves like different shells. It can be run
to behave as a Bourne shell (bash +B) or as a POSIX-compliant shell (type bash --posix), for
example, enabling it to read configuration files that are specific to those shells and run initialization
shell scripts written directly for those shells, with a greater chance of success.
Pages:
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170