Syntax error when "cp" statement with extended globbing options is moved to an "if" block

Question

Having some trouble doing a copy in Bash. This works fine:

# Enable extended globbing and include filenames beginning with a '.'
shopt -s extglob dotglob
# Copy git repo to expected place
cp -r !($YOCTO_DIR) $POKY_DIR/$GIT_REPO_NAME/

But when I put an if statement round it:

if [ -z "$FROM_JENKINS" ]; then
    # FROM_JENKINS is blank, this is a local build

    # Enable extended globbing and include filenames beginning with a '.'
    shopt -s extglob dotglob
    # Copy git repo to expected place
    cp -r !($YOCTO_DIR) $POKY_DIR/$GIT_REPO_NAME/
fi

I get:

./build.sh: line 80: syntax error near unexpected token `('

Line 80 is the cp. If I remove the brackets it works:

    cp -r . $POKY_DIR/$GIT_REPO_NAME/

Why does the if statement not like brackets in cp?

Answer 1

The problem are the order and "range" of reading and executing.

The whole if block is just one command. So the shell has to read until the end of this command before it executes it.

That means that the rules WITHOUT shopt -s extglob dotglob (I am referring to the line here, not all of its content; as ilkkachu points out in the comment: the dotglob is not relevant for the problem) are valid until the end of the if block because the shopt is executed afterwards only. And without the shopt -s extglob the !( is illegal there.

So you have to move the shopt before the if (and may revert it in an else branch).