Question

How could I split the long valueX string in the following bash code?

case "$1" in
    value1|value2|value3|...........more values..................| valueN)
        some_processing "$@"
        ;;
    ...
esac

I’m looking for splitting into separate lines.
M.b. like:

VAL+=value1
VAL+=value2
....

Answer 1

From the man page:

A case command first expands word, and tries to match it against each pattern in turn, using the same matching rules as for path‐name expansion[.]

In other words, it’s a glob pattern, not a regular expression. As such, you can use IFS between pattern tokens. For example:

case "$1" in
    value1 | \
    value2 )
        :
    ;;
esac

Note that you must escape the line continuation with a backslash, unlike the usual case where the pipe symbol will continue the line automatically. Other than that, you can break up the line the same way you would at the prompt.