add bash-scripting-guidelines.md

Author: E-Fir

bash-scripting-guidelines.md

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+Bash scripting guidelines
+=========================
+
+## Interpreter
+
+For better portability be sure to specify the interpreter in this way:
+```shell
+#! /usr/bin/env bash
+```
+
+## Set options
+
+For prevent hidden bugs use `set -euox pipefail` as the first command 
+when possible.
+For additional info, please see
+[manpages](http://manpages.ubuntu.com/manpages/hirsute/en/man1/set.1posix.html)
+
+## Variables
+
+Variables local to the script must be in the lower case.
+
+Using variable is allowed only wrapped in `"${}"`.
+Example:
+```shell
+var=123
+echo "${var}"
+```
+
+If you need to use `"$@"`, always use quotation marks.
+Example:
+```shell
+lua test/test.lua "$@"
+```
+
+If the script is sensitive to the current directory, store it in the `ROOT`
+variable. Example:
+```shell
+ROOT="${BASH_SOURCE[0]}"
+if([ -h "${ROOT}" ]) then
+  while([ -h "${ROOT}" ]) do ROOT=`readlink "${ROOT}"`; done
+fi
+ROOT=$(cd `dirname "${ROOT}"` && pwd)
+```
+
+## Wrapping other programs
+
+If the script is a wrapper around another program and no postprocessing is 
+needed after execution of that program, you should strive to replace the shell 
+without creating additional processes, using `exec`. Execution of the wrapper 
+script will be terminated after the `exec` call.
+Example:
+```shell
+exec /usr/bin/env "${LE_LUA_INTERPRETER}" "$@"
+```