unexpand:tldr:59ded

The command "unexpand -t ${number} ${filename}" is used to replace leading sequences of spaces in a file with the corresponding number of tabs.

Here's the breakdown of each part of the command:

• "unexpand": This is the command itself, which unexpands files by replacing spaces with tabs.
• "-t ${number}": The "-t" option specifies the tab width, and "${number}" is the desired number of spaces to be replaced by a single tab. For example, if "${number}" is set to 4, then 4 spaces will be replaced by one tab.
• "${filename}": This is the name of the file you want to unexpand. You would replace "${filename}" with the actual name of the file you want to operate on.

Overall, this command is particularly useful for converting files with leading spaces into tab-indented format, which is often desired in programming or code-related scenarios.