To convert uppercase characters to lowercase in a shell script, you can use the tr command with the -d and -s options.
For example, to convert a string stored in the FOO variable to lowercase, you can use the following command:
FOO=$(echo $FOO | tr '[:upper:]' '[:lower:]')
This will use the tr command to translate all uppercase characters in the FOO variable to lowercase characters and store the result in the FOO variable.
The -d option tells tr to delete characters that are specified in the first set but not in the second set. The -s option tells tr to replace multiple occurrences of a character with a single occurrence.
The [:upper:] and [:lower:] notation is used to specify character classes. The [:upper:] class includes all uppercase characters, and the [:lower:] class includes all lowercase characters.
You can also use the tr command to convert multiple strings at once. For example:
FOO=$(echo $FOO | tr '[:upper:]' '[:lower:]') BAR=$(echo $BAR | tr '[:upper:]' '[:lower:]') BAZ=$(echo $BAZ | tr '[:upper:]' '[:lower:]')
This will convert the FOO, BAR, and BAZ variables to lowercase.
Keep in mind that the tr command only works with ASCII characters. If you need to convert non-ASCII characters to lowercase, you may need to use a different approach, such as using the awk command or the sed command.