How To Constrain Command Line Application Columns

When working with command-line applications on ultra-wide monitors, the output can often stretch across the entire screen, making it difficult to read and follow. Many users, including myself, have encountered situations where commands like less -S produce lines that extend far beyond the visible area, negating the benefits of line wrapping. This leads to a less-than-ideal user experience, as it requires excessive horizontal scrolling to view the complete output. The core question then arises: Is there a way to constrain the available columns for command-line applications? This article delves into various methods and techniques to limit column width in the terminal, ensuring better readability and usability, especially on wide screens.

The Problem: Wide Output on Wide Monitors

Modern wide and ultrawide monitors offer increased screen real estate, which is a boon for multitasking and productivity in graphical user interfaces. However, command-line applications, designed primarily for text-based output, don't always adapt well to these wider displays. The default behavior of many command-line tools is to utilize the full terminal width, leading to long lines that can be cumbersome to read. Consider the scenario where you're viewing a log file using less -S. On a standard-width monitor, the -S option truncates lines that exceed the screen width, allowing you to scroll horizontally. However, on an ultrawide monitor, these lines can become excessively long, making it difficult to keep track of the content. Similarly, commands that produce tabular output, such as ps or ls -l, can generate columns that spread across the entire display, requiring significant eye movement and making comparisons challenging.

This issue is not merely aesthetic; it directly impacts usability and efficiency. Reading long, unbroken lines strains the eyes and makes it harder to identify patterns or errors in the output. Moreover, the need for constant horizontal scrolling disrupts the natural flow of reading and can lead to missed information. For users who spend a significant amount of time in the command line, these small inconveniences can accumulate and significantly reduce productivity. Therefore, finding effective ways to constrain the output width of command-line applications is crucial for enhancing the user experience and optimizing workflow.

Solutions for Constraining Columns

Fortunately, there are several approaches to address the problem of overly wide command-line output. These solutions range from using built-in terminal features to employing external tools and techniques. Let's explore some of the most effective methods:

1. Terminal Resizing and Window Management

The simplest and most intuitive method to constrain column width is to adjust the size of the terminal window itself. By reducing the width of the terminal window, you effectively limit the number of columns available to the application. This approach is particularly useful for commands that dynamically adapt to the terminal size, such as less or man. Most terminal emulators allow you to resize the window by dragging its edges or corners. Additionally, window management tools available in many operating systems can be used to precisely control the size and position of terminal windows.

For example, on macOS, you can use the built-in window tiling features or third-party applications like Spectacle or Magnet to quickly resize and position terminal windows. On Windows, the Windows key + arrow keys shortcut provides a convenient way to snap windows to different parts of the screen. Linux users have a variety of window managers and tiling window managers at their disposal, offering advanced window management capabilities. While resizing the terminal window is a straightforward solution, it can become tedious if you frequently need to switch between different column widths. Moreover, it doesn't provide a permanent or application-specific solution.

2. The COLUMNS Environment Variable

A more programmatic approach to controlling column width is by using the COLUMNS environment variable. This variable is recognized by many command-line applications and utilities, including less, man, and awk. By setting the COLUMNS variable to a specific value, you can override the terminal's reported width, effectively limiting the output to the specified number of columns. This method is particularly useful when you want to ensure consistent output across different terminals or when working in environments with varying screen sizes.

To set the COLUMNS variable, you can use the export command in most Unix-like shells (e.g., Bash, Zsh). For example, to limit the output to 80 columns, you would use the command export COLUMNS=80. This setting will persist for the current shell session. To make the change permanent, you can add the export command to your shell's configuration file (e.g., .bashrc, .zshrc). When using the COLUMNS variable, it's important to remember that some applications may not fully respect this setting. However, many core utilities and tools are designed to adapt to the COLUMNS variable, making it a valuable tool for controlling output width. Furthermore, you can temporarily override the COLUMNS variable for a single command by prefixing the command with the variable assignment, like so: COLUMNS=120 ls -l. This approach allows for fine-grained control over output width on a per-command basis.

3. Using fold and fmt Utilities

The fold and fmt utilities are powerful tools for manipulating text and wrapping lines in the command line. The fold command is specifically designed to wrap lines at a specified width, while fmt offers more advanced text formatting capabilities, including line wrapping, indentation, and paragraph formatting. These utilities can be used to pre-process the output of other commands, ensuring that the text fits within a desired column width.

For instance, to wrap the output of the ls -l command at 80 columns, you can use the pipeline ls -l | fold -w 80. The -w option in fold specifies the maximum line width. Similarly, you can use fmt to format text with more sophisticated options, such as adjusting indentation and preserving paragraph structure. For example, you might use cat long_text_file.txt | fmt -w 70 to format a long text file to a 70-column width. The key advantage of using fold and fmt is their versatility. They can be integrated into complex pipelines and scripts to ensure consistent text formatting across various commands and applications. However, they do require an extra step in the command execution, which might be slightly less convenient than directly controlling the output width of the original command.

4. Pagers with Line Wrapping

Pagers like less and most are essential tools for viewing long text files and command output in the terminal. While less -S truncates lines, other options can be used to enable line wrapping and control how the text is displayed. For example, using less -r will display raw control characters, which can sometimes affect line wrapping. Alternatively, omitting the -S option in less will often result in default line wrapping behavior, but the appearance can vary depending on the terminal and file content. The most pager is another powerful alternative that often provides better default line wrapping and customizable options for controlling text display.

To effectively use pagers for controlling column width, it's crucial to understand their configuration options and how they interact with terminal settings. For less, the environment variable LESS can be used to set default options. For example, setting export LESS='-R' in your shell configuration file will make the -R option the default behavior for less, which can sometimes improve line wrapping. The most pager is highly configurable through its configuration file, typically located at ~/.mostrc. By customizing the most configuration, you can fine-tune line wrapping, color schemes, and other display settings to suit your preferences. Using pagers with proper line wrapping configurations is a practical approach for viewing long output in a readable format, especially when dealing with text files or command output that doesn't require strict column alignment.

5. Using tmux or screen for Pane Management

Terminal multiplexers like tmux and screen are powerful tools for managing multiple terminal sessions within a single window. They also provide excellent capabilities for pane management, allowing you to split the terminal window into smaller, independent regions. By creating horizontal or vertical panes, you can effectively constrain the available columns for each command-line application running within a pane. This approach is particularly useful when you need to work with multiple commands simultaneously and want to ensure that their output remains within a manageable width.

To use tmux for pane management, you can start a new session by typing tmux in the terminal. Within a tmux session, you can split the current pane horizontally by pressing Ctrl+b followed by `%