nkf:tldr:d3d59

The command nkf -m --overwrite ${filename-txt} is using the nkf utility with some specified options and an argument.

Explanation:

• nkf stands for "Network Kanji Filter" and is a command-line utility used to convert text files between different character encodings.
• -m is an option that tells nkf to automatically detect the character encoding of the input file.
• --overwrite is an option that tells nkf to overwrite the original file with the converted content.
• ${filename-txt} is the argument that specifies the file to be processed. It should be replaced with the actual filename, including the extension (e.g., file.txt).

Overall, this command is likely used to convert the character encoding of a text file, based on its contents, and then overwrite the original file with the converted result.