Lightweight template tool for Linux shell

tcat means cat shell template files.

Think about tcat as a tool similar to zcat. cat prints the contents of input files. zcat first unzips the zip files, then prints their contents. tcat first replaces the variable name with their values in the input template files, then prints the rendered contents.

Usage

tcat accepts one ore more template files as input, and writes output to STDOUT after replacing variables with their values. If no template files are specified, it reads input from STDIN by default.

tcat.sh [template-file ...]

All variables in template files must be defined and visible from within the script, otherwise the command will fail.

Examples

Read from STDIN

$ echo "My name is \${USER}" | ./tcat.sh

Output:

My name is functicons

Note that in this example, we don't need to explicitly define USER, because it is a predefined shell environment variable. Also we should use \${USER} instead ${USER}; otherwise, the variable will be replaced by echo before it reaches tcat.

Read from template files

Template file:

Hello ${name}!

Sentence: ${sentence}

Escape: \${foo}

Quote: "foo" 'bar'

Environment variable \${USER}: ${USER}

Optionally, you could define variables in a properties file:

name=world
sentence="this is a sentence"

Then start a child process, load and export variables, render the template:

$ (source examples/properties; export $(cut -d= -f1 examples/properties); ./tcat.sh examples/template)

Output:

Hello world!

Sentence: this is a sentence

Escape: ${foo}

Quote: "foo" 'bar'

Environment variable ${USER}: functicons