shlib

One of the great drawbacks to the POSIX shell environment is that, like the C programming language, it has very little in the way of builtin high-level functionality. To do many things often requires resorting to esoteric hacks which wrap other tools. This has lead to a number of variations of the POSIX shell (Korne Shell, Z Shell, Bash, etc..) which implement various high-level features in their own proprietary way. shlib aims to supply many (all?) of these high-level features using only pure POSIX shell syntax, while optimizing the core of any interface via shell-specific enhancements under the covers (making afore mentioned esoteric hacks totally portable and useful for all). Further more, shlib is self-optimizing at load-time, meaning that it does not spend time checking the shell environment every time an interface is called. The end result is fast and portable shell scripts which work right regardless of which flavor of /bin/sh is interpretting them.

Philosphy

shlib is written around the goal of providing a portable dumping ground for various shell tricks and hacks produced throughout the ages. Such things as floating point arithematic, string manipulation, and even just overly common routines used by programmers on a day-to-day basis. With that in mind, shlib is a framework which presents a portable interface to the developer, but which may be implemented via any number of methods under-the-covers at load time.

What shlib is not

shlib is not in and of itself a scripting language, or a replacement to existing shells. While various libaries w/in shlib may implement an interface using external utilities are shell-specific features, the interfaces provided conform to the Shell Command Language as defined by the OpenGroup.

load-time optimization

Due to the nature of POSIX shell, libraries can perform tests when they are imported, as opposed to doing a test every time an interface is called. This allows shlib to implement a single interface via a variety of methods, and select the method which best fits the local platform.

For example:

	#!/usr/bin/env shlib
	
	if shlib.hascmd seq; then
		__math_seq() { command seq "${@}"; }
	else
		# no seq cmd available then attempt to load the bash version
		# which uses a c-for style itterator, else use one written in
		# pure POSIX shell.
		if ! . seq.bash > /dev/null 2>&1; then
			. seq.sh
		fi
	fi
	alias math.seq='__math_seq '
	
	shlib.main() { math.seq "${@}"; }

From here a program only need to import math.seq to gain access to a math.seq() function which will call the native seq command if available, otherwise it will use one implemented in POSIX shell.

Usage

shlib tries hard to be as non-intrussive as possible to software developers. To this end there are a number of ways to integrate shlib into ones software.

Command Line

shlib can be envoked from the command-line in much the same way as traditional /bin/sh.

Examples:

1. Run an shlib: shlib program.shlib
2. Run a shell script: shlib program.sh
3. Shell-like -c syntax: shlib -c 'import hostinfo;hostinfo'

See shlib --help for various command-line options which change the behavior of shlib.

hash/bang

You can make shlib the interpretter for an existing shell script.

#!/usr/bin/env shlib

(warning: not all OS's support scripts being used as the interpretter for a file in this way).

Source in shlib

When all else fails, you can simply source in the shlib top-level script into your existing /bin/sh scripts.

. /path/to/shlib

See Also

• Examples
• Development
• API Reference
• Future features
• License