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Top Forums Shell Programming and Scripting Tip: template for a safe and portable script Post 303032522 by MadeInGermany on Tuesday 19th of March 2019 02:47:02 PM
Old 03-19-2019
Tip: template for a safe and portable script

In an attempt to finally end this article I start this new thread.
Here is a template for a safe and portable script.
Code:
#!/bin/bash
# /bin/bash exists on most still supported Unixes
#
# tr and date behave better with
if [ -n "$LC_ALL" ]; then export LC_ALL=C; else export LANG=C; fi
#
# Unix optional packages install in
opt_path=/usr/local/bin
solaris_opt_path=/usr/sfw/bin:/opt/csw/bin
#
# set PATH so no PATH is inherited, export it to all children
# Solaris is Posix-compliant in /usr/xpg4/bin and BSD-compliant in /usr/ucb
export PATH=/usr/xpg4/bin:/bin:/usr/bin:/sbin:/usr/sbin:/usr/ucb:${opt_path}:${solaris_opt_path}
#
# HP-UX is Posix-compliant with
export UNIX95=
#
# GREP_OPTIONS can obscure GNU grep
unset GREP_OPTIONS
#
# LD_* can obscure external commands
unset LD_LIBRARY_PATH LD_PRELOAD
#
# no glob file-matching in command args and word lists (for loop)
set -f
#
# prefer builtin commands and use Posix-compliant options
# check with "shellcheck"

Ok this is my wisdom. Perhaps you want to add something from your wisdom?
 
XT-CREATE-XEN-CONFIG(8) 				 Perl Programmers Reference Guide				   XT-CREATE-XEN-CONFIG(8)

NAME
xt-create-config - Create a Xen configuration file for a new guest SYNOPSIS
xt-create-config [options] Filename Options: --output Specify the output directory to use. --extension Specify the file extension to use. General Options: --admins Specify some administrator accounts which should be created for use by the xen-shell. --template Specify the template file to use when creating the Xen configuration file. Help Options: --help Show this scripts help information. --manual Read this scripts manual. --version Show the version number and exit. Debugging Options: --verbose Be verbose in our execution. All other options from xen-create-image, such as the new IP address(es) to give to the new instance, will be passed as environmental variables. ABOUT
This script is invoked by xen-create-image after it has created and customised a new Xen guest. It is responsible for creating the configuration file which Xen will use to start the instance. The configuration file will be created in the directory /etc/xen using a template file to determine how the configuration file should be created. By default the script will use /etc/xen-tools/xm.tmpl as its input. INVOCATION
This script will be invoked by the xen-create-image script, rather than directly. This is because it will expect to receive the values to insert into the output template in as environmental variables. You could execute it manually via a long command line, but that is error-prone and probably not useful: hostname=foo.my.flat ip=192.168.1.2 ... xm-create-xen-config --output=/etc/xen --template=/etc/xen-tools/xm.tmpl ARGUMENT PASSING
This script will be invoked with a full copy of the arguments from xen-create-image in its environment, along with several command line arguments. This has several implications for customization. If you wish to setup a new variable in the output template such as "foo=bar" you could update the script to include "${foo}", then invoke xen-create-image with this environmental variable set. $ foo=bar xen-create-image --hostname=test.my.flat ... The environment will be duplicated/inheritted by this script when it is executed, and your variable will be included in the output file. For details on the template file syntax please see the documentation for the "Text::Template" perl module. (If you have the perldoc package installed you can read this with "perldoc Text::Template".) AUTHORS
Steve Kemp, http://www.steve.org.uk/ Axel Beckert, http://noone.org/abe/ StA~Xphane Jourdois LICENSE
Copyright (c) 2005-2009 by Steve Kemp, (c) 2010-2012 by The Xen-Tools Development Team. All rights reserved. This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The LICENSE file contains the full text of the license. 4.3.1 2012-06-30 XT-CREATE-XEN-CONFIG(8)
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