How to use the command 'yank' (with examples)

Yank is a versatile command-line tool designed to facilitate the process of copying text from terminal output using a selection interface. It reads input from the standard input (stdin), presents a selection interface that allows users to choose specific text, and then copies this selection to the clipboard. Yank is particularly useful for quickly extracting pieces of information from long command outputs without the need for mouse interactions.

Use case 1: Yank using the default delimiters (\f, \n, \r, \s, \t)

Code:

sudo dmesg | yank

Motivation:

This example is helpful when you want to review and copy specific parts from lengthy system logs generated by the dmesg command. System logs can be extensive, and using Yank helps quickly isolate and copy relevant information directly to your clipboard, especially when troubleshooting or documenting system issues.

Explanation:

• sudo dmesg: This command outputs kernel ring buffer messages, usually useful for debugging kernel-level issues. The sudo command is used to ensure you have the necessary permissions to view complete log details.
• | yank: This pipes the dmesg output into Yank. Yank will then display the output with sections divided by default delimiters such as space (\s) or newline (\n), allowing you to select a specific section to copy.

Example Output:

While I can’t display text selected from a clipboard operation in real-time here, using yank would typically open an interface showing segments like [12.345678] indicating timestamps, log levels like INFO, and error messages, which you can navigate through and select to copy.

Use case 2: Yank an entire line

Code:

sudo dmesg | yank -l

Motivation:

This is useful in scenarios where entire lines from the command output are significant and must be copied without omissions. For instance, full log entries sometimes contain complex information spread across multiple fields/characters that should be captured as a whole for accurate analysis or reporting.

Explanation:

• sudo dmesg: Outputs kernel messages, as before.
• | yank -l: The -l flag tells Yank to consider the entire line as a single selection unit. This is beneficial when line-by-line integrity in the copied text is necessary.

Example Output:

Running this command would allow you to select entire log entries like:

[12.345678] kernel: INFO: task cardinal:1234 blocked for more than 120 seconds.

Selecting one ensures you have the entire entry in context to analyze further or highlight for reporting purposes.

Use case 3: Yank using a specific delimiter

Code:

echo hello=world | yank -d =

Motivation:

This use case effectively demonstrates how to copy sections of text that are delimited by a specific character. When working with configuration files, environment variables, or any text data where a particular delimiter signifies component parts, this feature helps quickly isolate these parts for copying and subsequent manipulation or inspection.

Explanation:

• echo hello=world: Outputs a simple string with a = delimiter.
• | yank -d =: Here, the -d option specifies = as the delimiter. Yank will split the input at = and allow you to select either side of the delimiter to copy.

Example Output:

The Yank interface will let you choose between hello and world, making it simple to, for example, copy just the variable name or its value from an assignment operation.

Use case 4: Only yank fields matching a specific pattern

Code:

ps ux | yank -g "[0-9]+"

Motivation:

When analyzing system processes, it might be important to quickly extract numeric information such as process IDs or memory usage statistics. This use case focuses on filtering down vast process-related outputs to only extract these numeric details based on a specific pattern.

Explanation:

• ps ux: Outputs detailed information about user processes, including PID, CPU usage, memory usage, etc.
• | yank -g "[0-9]+": The -g flag uses a regular expression to match specific patterns—in this case, sequences of digits. Yank will only present fields matching this pattern for selection, filtering out irrelevant text.

Example Output:

The Yank interface might focus on numeric values only, letting you select and copy sequences such as 1234 which could represent PIDs or memory sizes like 450.

Conclusion:

The yank command is a valuable tool for command-line users, providing an intuitive way to extract and copy specific parts of command outputs efficiently. By allowing users to define delimiters, match patterns, or select entire lines, it adapts to various use cases from log analysis to system process inspection, enhancing productivity and precision when dealing with textual data in a terminal environment.