The “sed: re error: illegal byte sequence” error occurs when the sed command encounters an illegal byte sequence in the input data. This error is commonly seen when dealing with text files containing non-ASCII characters, such as special characters or characters from non-English languages.
To understand this error better, let’s consider an example. Suppose we have a file named “data.txt” with the following content:
Line 1: Hello World!
Line 2: Café au Lait
If we try to run a sed command to replace “Hello” with “Hi” in “data.txt” using the following command:
sed 's/Hello/Hi/' data.txt
We will encounter the “sed: re error: illegal byte sequence” error because the “é” character in “Café au Lait” is not a valid ASCII character. The sed command is expecting valid ASCII characters by default, so it fails to handle this input.
To fix this error, we need to specify the correct encoding for the sed command to handle non-ASCII characters. One common encoding used is UTF-8. We can set this encoding using the LANG environment variable before running the sed command.
Here’s an updated version of the sed command that sets the LANG variable to UTF-8:
LANG=en_US.UTF-8 sed 's/Hello/Hi/' data.txt
By specifying the correct encoding, the sed command can now handle the “é” character without encountering the error.