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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?
 
env(1)								   User Commands							    env(1)

NAME
env - set environment for command invocation SYNOPSIS
/usr/bin/env [-i | -] [name=value]... [utility [arg... ]] /usr/xpg4/bin/env [-i | -] [name=value]... [utility [arg... ]] DESCRIPTION
The env utility obtains the current environment, modifies it according to its arguments, then invokes the utility named by the utility op- erand with the modified environment. Optional arguments are passed to utility. If no utility operand is specified, the resulting environment is written to the standard output, with one name=value pair per line. /usr/bin If env executes commands with arguments, it uses the default shell /usr/bin/sh (see sh(1)). /usr/xpg4/bin If env executes commands with arguments, it uses /usr/xpg4/bin/sh (see ksh(1)). OPTIONS
The following options are supported: -i | - Ignores the environment that would otherwise be inherited from the current shell. Restricts the environment for utility to that specified by the arguments. OPERANDS
The following operands are supported: name=value Arguments of the form name=value modify the execution environment, and are placed into the inherited environment before utility is invoked. utility The name of the utility to be invoked. If utility names any of the special shell built-in utilities, the results are unde- fined. arg A string to pass as an argument for the invoked utility. EXAMPLES
Example 1 Invoking utilities with new PATH values The following utility: example% env -i PATH=/mybin mygrep xyz myfile invokes the utility mygrep with a new PATH value as the only entry in its environment. In this case, PATH is used to locate mygrep, which then must reside in /mybin. ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of env: LANG, LC_ALL, LC_CTYPE, LC_MES- SAGES, and NLSPATH. PATH Determine the location of the utility. If PATH is specified as a name=value operand to env, the value given shall be used in the search for utility. EXIT STATUS
If utility is invoked, the exit status of env is the exit status of utility. Otherwise, the env utility returns one of the following exit values: 0 Successful completion. 1-125 An error occurred. 126 utility was found but could not be invoked. 127 utility could not be found. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: /usr/bin +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |CSI |enabled | +-----------------------------+-----------------------------+ /usr/xpg4/bin +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWxcu4 | +-----------------------------+-----------------------------+ |CSI |enabled | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
ksh(1), sh(1), exec(2), profile(4), attributes(5), environ(5), standards(5) SunOS 5.11 2 Jan 2002 env(1)
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