My new book,
Pro Bash Programming: Scripting the GNU/Linux Shell
has just been published (2009-10-19).
I wrote Pro Bash Programming as a tutorial that introduces the
shell, and bash specifically, as a programming language.
It covers everythying from the traditional first program in any
language, "Hello, world!", to functions, to reading function keys
and the mouse.
The shell referred to in these pages is always a Bourne-type shell;
that is, a shell whose syntax is based on the Unix
shell introduced by Steven Bourne in 1978 (or thereabouts), with
some later improvements. On all Unix systems, a Bourne-type shell
can be found in /bin/sh. On most modern systems, this will be somewhat
better than the Bourne shell — it will be a POSIX shell. If it
is not, there should be a POSIX-compliant shell elsewhere on the
system.
A POSIX shell is a Bourne shell with a number of extensions (which
are mostly derived from the Korn
Shell). The most important ones perform string manipulation and
integer arithmetic. In a Bourne shell, arithmetic operations require
an external program (e.g., expr, awk or
bc) as does finding the length of a string, or cutting
a string into pieces. POSIX has $((...)) for integer
arithmetic and parameter expansions for string operations.
Generally, scripts and snippets published here are designed to run in a POSIX shell. Some will run in a Bourne shell, and those that will not should not be hard to convert (in the unlikely event that you find it necessary). A few scripts require added extensions found in bash and ksh.