tr command Illegal byte sequence error

Troubleshoot `tr` command “Illegal Byte Sequence” Error in Linux

Estimated reading time: 2 minutes

The tr command in Linux is used to translate or delete characters from a text stream. However, when it encounters an invalid or unexpected byte sequence, it throws an “Illegal byte sequence” error. This usually happens when the input data contains characters that do not match the expected encoding.

Example of tr command “Illegal Byte Sequence” Error

Let’s take, for example, a scenario where you attempt to translate lowercase letters to uppercase using the tr command:

For most inputs, this works perfectly. However, if your input contains non-ASCII characters, you might encounter the “Illegal byte sequence” error:


Now, why did this error occur? Some of the most common causes are:

  • Encoding Mismatch: The input data might be in a different encoding than what the tr command would be expecting.
  • Non-ASCII Characters: Special characters or symbols not supported by the tr command’s default settings may exist in the input.

SOLVED: tr “Illegal byte sequence” Error

Step 1: Set the Locale

As noted above, one of the common reasons for the tr command throwing an “Illegal byte sequence” error is a mismatch of encoding settings. Setting the locale can often resolve the encoding mismatch. Use the following command to set the locale to UTF-8:

Step 2: Re-run the tr command after setting the locale:

Alternatively, you can also run both commands in one go:

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