htmlencode

CLI encoder and decoder for HTML entities

Description

A command-line tool for encoding and decoding HTML entities, similar to base64 or urlencode. Converts special characters like <, >, &, ", ' to their HTML entity equivalents (<, >, &, ", ') and vice versa.

Build

Autotools Build

./autogen.sh && ./configure && make

Then sudo make install to install to /usr/local/bin

Direct Compilation

gcc -Wall -Wextra -pedantic -O2 -s -o htmlencode src/main.c

Usage

Reads from standard input, writes to standard output.

Options

• -a encode all characters (using numeric entities)
• -b do not automatically encode non printable (i.e. binary) characters
• -c specify a different set of special characters when encoding
• -d decode data
• -l encode input line by line
• -n do not output the trailing newline when encoding
• -x use hexadecimal entities (&#xHH;) instead of decimal (&#NNN;)
• -h display help and exit

Examples

Encode HTML:

echo '<script>alert("XSS")</script>' | htmlencode

Output: <script>alert("XSS")</script>

Decode HTML:

echo '<script>alert("XSS")</script>' | htmlencode -d

Output: <script>alert("XSS")</script>

Encode all characters as numeric entities:

echo "Hello" | htmlencode -a

Output: Hello

Use hex entities:

echo "<test>" | htmlencode -ax

Output: <test>

Features

• Named entities: Common characters (<, >, &, ", ') are encoded as named entities by default
• Numeric entities: Can encode any character as decimal (&#NNN;) or hex (&#xHH;) numeric entities
• Decode support: Full decoding of both named and numeric (decimal/hex) entities
• Line mode: Process input line by line with -l
• Binary safe: Automatically encodes non-printable characters (unless disabled with -b)

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.