execute command from the terminal vs from a script - path with wildcard - prevent glob expansion - linux

Question

I experience a strange problem and I think it have something to do with file/directory globbing
script
echo "tar -zcvf $file $base/$target $exclude_args"
cd $base && tar -zcvf $file $base/$target $exclude_args
output
tar -zcvf www_2017-04-24.tar.gz /var/www --exclude '/var/www/bak/*/*' --exclude '/var/www/test'
When running the script the exclude path is omitted (every directory is gzipped)
When running the output directly from putty the directories under /var/www/bak/*/* is excluded from the gzip
update
parse_exclude_paths (){
# escape forward slashes to avoid the paths to expand
args=$(echo "$exclude" | sed 's,/,\\\/,g')
args=$(printf " --exclude '%s'" $args)
# strip escapes
echo "$args" | sed 's,\\\/,/,g'
}
exclude="/var/www/bak/*/* /var/www/test"
exclude_args=''
if [ ! -z "$exclude" ]; then
exclude_args="$(parse_exclude_paths "$exclude")"
fi
update 2
If the command is sent via SSH there is no problems and the exclude paths are excluded from the gzip
ssh root#$host 'cd '"$base"' && tar -zcvf $file '"$base/$target $exclude_args"

Answer 1

I snooped your question history and saw that you're familiar with PHP. Here's the equivalent problem in PHP:
function foo($arg1, $arg2) {
echo "You passed $arg1 and $arg2\n";
}
$var='"one", "two"';
echo "Running: foo($var);\n";
foo($var);
The echo prints Running: foo("one", "two"); and that command works just fine if you copy-paste it!
Why does foo($var); instead write PHP Warning: Missing argument 2 for foo()?
The answer is of course that literal quotes in your variables don't matter for how the function is called. This is the same in both PHP and shell.
The solution in both PHP and Bash is to use an array:
#!/bin/bash
file="www_2017-04-24.tar.gz"
base="/var"
target="www"
exclude_args=( --exclude '/var/www/bak/*/*' )
cd "$base" && tar -zcvf "$file" "$base/$target" "${exclude_args[#]}"
sh is more primitive and doesn't support arbitrary arrays, but we can reuse the positional parameters to the same effect:
#!/bin/sh
file="www_2017-04-24.tar.gz"
base="/var"
target="www"
set -- --exclude '/var/www/bak/*/*' # Now assigned to $1, $2, etc
cd "$base" && tar -zcvf "$file" "$base/$target" "$#"
Another option is to use eval to re-interpret a string as a shell command. This means that anyone who can influence your variables can take over your system, but that may be ok if all the variables come from users with equivalent privileges:
eval "tar -zcvf $file $base/$target $exclude_args"