Shell Programming and Scripting

Writing scripts is software development - programming - so all the do's and dont's of programming apply.

Programming is in my experience mostly about bringing your thought process into order. It always helped me to standardise and conventionalise as much as i can: i have a system for naming variables so that the name immediately tells me what it should contain and what type it is (note that shell variables aren't really typed but if you try to multiply a string by 5 it still leads to an error). I have a naming convention for my functions so i cannot name two functions the same name. And so on, and so on.

Picture programming as building a house but with the twist that you have to build the bricks for that first: if your bricks are all neat cubes or cuboids it is easy to build straight walls and it is equally easy to foresee if the wall will hold or not. If your bricks are all irregular shapes your walls will be equally irregular shapes and it might be impossible to calculate if they are going to hold or not until they come crushing down.

To be honest i have no idea what your question is. Please explain again. If it is a new question and unrelated to the topic of this thread please open a new thread. We like to organise our threads so that they are about one topic only.

In Korn shell i have built myself a "library" using the FPATH variable and strive to write my functions in a way so that they can be included in this library if possible. When i started programming one of the first things i learned is write your functions always in a way so that they can be put into a library and i still try to adhere to that.

I also have a standard header for my function files which you might want to adopt/adapt. I always found it useful to have a standard format for documentation so that i know immediately where to look for specific information (like with man pages). As i use the same header for functions and scripts i have a "USAGE"-part for the user documentation and a "DOCUMENTATION"-part for the internal documentation:

Code:

# ------------------------------------------------------------------------------
# template.ksh                               template for ksh scripts/functions
# ------------------------------------------------------------------------------
# Author.....: 
# last update: 0000 00 00    by:
# ------------------------------------------------------------------------------
# Revision Log:
# - 0.99   0000 00 00   Revision title
#                       Revision description
#
# ------------------------------------------------------------------------------
# Usage:
#
#     Example:
#
# Prerequisites:
#
# ------------------------------------------------------------------------------
# Documentation:
#
#     Parameters:
#     returns:
# ------------------------------------------------------------------------------
# known bugs:
#
#     none
# ------------------------------------------------------------------------------
# ..............................(C) 2018 bakunin ...............................
# ------------------------------------------------------------------------------

I hope this helps.

bakunin

I can understand that you prefer ksh over bash in general, but I don't see how for this particular case, ksh would give an advantage over bash. I must admit that I'm not proficient at all in ksh, and would appreciate an explanation of this matter.

Thanks Bakunin.
I need to restate my "primary objective" was and still is to modify existing bash script,
I started with 2000+ lines and now it is doubled!

I realize I am asking stupid and basic questions, however I have no intention to make carrier out of writing bash scripts.

But I am thankful for all the support I have recieved so far.

Its a bit off-topic, but i'll bend the rules slightly for you, as it is (remotely) connected with the problem here:

In ksh there is a Variable FPATH, which works just like PATH for executables, but for functions. Once set the shell will seek undeclared functions along this path(es) like it would search for unqualified executables along the contents of the PATH variable. This makes it easy to create a directory with standardised functions used in many scripts - just like a library in high-level-languages. I use this mechanism a lot and have about 50 functions in my "library" which i use over and over. It makes organising (and improving!) ones work a lot easier than copying and pasting all the "standard stuff" from one script to the next.

Suppose you have 50 scripts where you have copied and pasted alls sorts of functions into. Now you come up with an (internal) improvement to one of those functions. Are you gonna copy and paste it again through all those scripts? I can improve my library functions easily and all scripts using it will profit from that immediately.

@annacreek
I said it above but you probably missed it: i do not understand what your question is. Please explain again what you want to achieve and I'll gladly help.

I hope this helps.

bakunin