bash-unsafe-templates (but.sh)

A rather unsafe, very trusting templating engine that lets you use bash as your parser.

Based on http://serverfault.com/questions/287688/templating-with-linux-in-a-shell-script/#699377

Prerequisites

but.sh requires only bash

Downloading

wget https://raw.github.com/nealian/bash-unsafe-templates/master/but.sh && chmod +x but.sh

Environment

The current shell environment is used, and additional variables may be set in two ways:

• As with any other script, you may specify variable values on the command line (FOO=bar ./but.sh)
• Additionally, environment files may be sourced with the -c and --config flags (and any filenames at the end of the arguments)

Templates

Templates are text files with bash expansions, and with escaped double-quotes and backslashes. but.sh will expand the following:

• $VAR and ${VAR} (and ${ARRAY[@]} and other more complicated variable expansions)
• $(()) arithmetic expansions
• Backtick (``) and paren-style ($()) command substitions

Literal character escapes (backslash-escapes):

Outside of expansions:

• ` may be printed in the output with \`
• $ may be printed in the output with \$
• " may be printed in the output with \"
• \ may be printed in the output unescaped in most cases
• If it is to be followed immediately by a `, a $, a ", a newline, or another \, it must be escaped with \\
• All other characters will be printed normally

These follow the rules of a bash here-document

Inside expansions:

• See the bash manual

Example

This repository includes an example template and its output. Additionally, this gist includes the template I actually initially built this for.

Usage

but.sh <template-file> [-o|--output <output-file>] [[[-c|--config] <config-file>] ...]