showrgb

showrgb [filename]

filename
    Optional path to an alternative RGB color database file. If this argument is provided, showrgb will read and display the contents of the specified file instead of the system's default RGB database. If omitted, the command defaults to using the standard system-wide rgb.txt file.

The showrgb command is a simple utility within the X Window System that prints the contents of the system's RGB color name database to standard output. This database, typically stored in a file like /usr/share/X11/rgb.txt or /etc/X11/rgb.txt, contains a mapping of thousands of human-readable color names (e.g., "red", "LightBlue", "DarkGreen") to their corresponding 8-bit RGB hexadecimal values.

Users primarily employ showrgb as a reference or diagnostic tool to quickly look up the exact numerical RGB values associated with specific named colors that X applications recognize. When invoked without any arguments, it processes the default system RGB file. If an optional filename is provided, it will read and display the contents of that specified file instead. Its output typically consists of three integer values (for Red, Green, Blue components) followed by the color name on each line.

showrgb provides no built-in filtering or search capabilities; it outputs the entire content of the RGB database. For specific color lookups or a subset of entries, its output is typically piped to other commands like grep (e.g., showrgb | grep LightBlue).

The command relies on the existence and correct formatting of the rgb.txt file. If the file is missing, corrupted, or in an unexpected location, showrgb may fail or produce an error message.

The primary RGB color database file that showrgb processes by default is typically located at /usr/share/X11/rgb.txt or /etc/X11/rgb.txt, depending on the specific Linux distribution and X11 installation. This file is crucial for X applications to correctly interpret named colors, mapping them to their corresponding numerical values.

showrgb is a fundamental utility that has been an integral part of the X Window System distribution since its early development. It emerged as a simple, yet indispensable tool for developers and users to reference the X color database. Its core functionality has remained largely unchanged over decades, reflecting its straightforward and consistent purpose within the X ecosystem.

rgb.txt(5): The manual page describing the format and content of the RGB color database file itself., xrdb(1): X resource database utility, which can load and query resources including color definitions used by X applications., xcolors(1): (If available) A graphical utility often used to display X color names and their values interactively., grep(1): A powerful command-line utility frequently used in conjunction with showrgb to filter its output and find specific color names or values.