shell case statement patterns...[SOLVED]

[Sadako]

Hi, I'm trying to use a case statement in a shell script to match a hexadecimal string.

Code: Select all

case "${FOO}" in
    [0-9a-eA-E]* ) echo BAR ;;
esac

This pretty much works, but it'll match anything that simply begins with a hex digit.

Supposedly, prefixing a pattern with '+' should make it match "one or more" occurances, which is exactly what I'm looking for, but I can't figure out how it should be used...

Code: Select all

case "${FOO}" in
    ( +([0-9a-eA-E]) ) echo FOO ;;
    +([0-9a-eA-E]) ) echo FOO ;;
    (+([0-9a-eA-E])) echo FOO ;;
    +([0-9a-eA-E]) echo EEE ;;
esac

Each of the above (tested separately) results in "syntax error near unexpected token `('".
Various quoting and putting the pattern in a variable hasn't worked, either...

I'm testing with both bash and dash atm, but would rather avoid any bash specific alternatives with '[[', and I am aware of potential locale issues with the [0-9a-eA-E] pattern.

Anyone know the correct syntax for this?

Thanks.

[Sadako]

Upon further reading, seems that '+(pattern)' for matching one or more relies on shopt -s extglob, meaning it's bash-specific, or at the very least not posix.

D'oh...

[mv]

POSIX shell patterns are not nearly as powerful as regular expressions.
In your case you can come through with negating:

Code: Select all

case ${FOO:-x} in
*[!0123456789abcdefABCDEF]*)
  echo "FOO not hex";;
esac

The :-x is there to make an undefined or empty string to be not considered as hex. Note that [!0-9a-fA-F] would be locale dependent which is probably not what you want. (BTW: "F" still is hex...)

[Sadako]

POSIX shell patterns are not nearly as powerful as regular expressions.
In your case you can come through with negating:

Code: Select all

case ${FOO:-x} in
*[!0123456789abcdefABCDEF]*)
  echo "FOO not hex";;
esac

The is there to make an undefined or empty string to be not considered as hex. Note that [!0-9a-fA-F] would be locale dependent which is probably not what you want.

I had return this

Code: Select all

PATTERN='[0-9a-fA-F]'

ishex() {
    [ -s "${1}" ] || return 1

    FOO="${1}"

    while [ ! "${FOO}" = "${FOO#${PATTERN}}" ]; do
    	FOO="${FOO#${PATTERN}}"
    done

    [ -z "${FOO}" ]
}

which got the job done, but that negation looks like a rather elegant solution I don't think I would have thought of myself, so tyvm for that.

However, I found BAR="$((0x${FOO}))" returns an error if the value isnt hex, and gives me the decimal value of it at the same time.

(BTW: "F" still is hex...)

Ahhhhhh! Brainfart! <.< >.>