Piping find to xargs works in terminal, but not in shell script [duplicate]

Question

I'm trying to write a Bash shell script that copies all the files in the current directory, minus a few exceptions, into another directory. The script builds a command, stores it in a variable, and runs it. Here's the baffling part: when the command it builds is run in a shell script, it fails with the message find: paths must precede expression: `|xargs' If I remove the space before the |, I instead see find: unknown predicate `-i' . But when I echo the command it builds and run it, it works fine! To make it even weirder, echo "$cmd"|bash fails with the same error message!

The script (synchronize.sh):

#! /bin/bash

EXCLUDED_FILES=(folder1 file.txt synchronize.sh)
FLAGS='-r'
PROJECT_NAME=project

TARGET_DIR=$HOME/Documents/IDE/$PROJECT_NAME/assets
cmd='find ./* -maxdepth 0'
cmd_end="|xargs -i cp -r {} -t $TARGET_DIR"

for file in ${EXCLUDED_FILES[@]}
do
    cmd+=" ! -name \"$file\""
done

cmd+=$cmd_end

$cmd               #Running the command directly fails
#echo  $cmd        #Yet copying and pasting the output of this command will work just fine
#echo "$cmd"|bash  #Though this inexplicably fails, with the same message as just $cmd

None of the files or folders have spaces in their name, or any special characters except underscores and periods.

Answer 1

So, in the answer linked by @KamilMaciorowski , I learned that Bash treats pipes differently in strings that run commands. I solved the problem by changing the line $cmd to eval "$cmd" and it works great now!

Be warned, eval can lead to code injection issues, but that's not relevant for this particular script.

Answer 2

You have a good idea about loading a list to a command, but there are better ways to combine variables and commands.

@KamilMaciorowski provided some good context here, but you're probably still hunting around for a more definitive answer. You can see a good example for using printf to format your array into the find command by reading more here.

What this will look like in your case would be something like this:

find ./* -maxdepth 0 $(printf "! -name %s " $EXCLUDED_FILES) -exec cp -r {} $TARGET_DIR \;