Valid commands to be used in backticks in bash?

Consider the two commands,

command1="mysql -umyuser -pmypassword -e \"show databases;\";"
command2="cat stackoverflow.txt"

The strings are formed as follows,

echo ${command1} -> mysql -umyuser -pmypassword -e "show databases;";
echo ${command2} -> cat stackoverflow.txt

My aim is to run the command from a variable and store it's result in another.

So what I do is,

result1=`${command1}`
ERROR 1049 (42000): Unknown database 'databases;";'

BUT,

result2=`${command2}`

works perfectly fine.

When using $() instead of backticks the commands behave the same.

Both, of these commands work perfectly fine when run directly in backquotes instead of a variable.

Why this different behaviour?

Solution

The following:

command1="mysql -umyuser -pmypassword -e \"show databases;\";"

fails because of word splitting. When you say $command1, the shell would interpret it as:

mysql -umuuser -pmypassword -e '"show' 'databases;";'

So the parameter passed to -e option is "show and not what you thought.

Make use of functions instead:

mycommand() {
  mysql -umyuser -pmypassword -e "show databases;"
}

In the second case, the shell is simply reading the contents of the file and executing it. As such, it works.