Rsync command variable, bash script - bash

Question

RSYNC="rsync -avzhe 'ssh -i /path/to/deploy_keys/id_rsa' --delete "
# Files
$RSYNC deploy#ip:/var/www/path1 /var/www/path1
$RSYNC deploy#ip:/var/www/path2 /var/www/path2
I'd like to introduce this RSYNC Variable to be more compact, but it throws an error:
Unexpected remote arg: deploy#ip:/var/www/path1
If i use only rsync inside the doublequotes, it works fine. For the sake of readability, i'd keep them separate command invocations.

Answer 1

I agree that eval is dangerous. In addition to the array approach #Eugeniu Rosca suggested, you could also use a shell function:
my_rsync() {
rsync -avzhe 'ssh -i /path/to/deploy_keys/id_rsa' --delete "$#"
}
my_rsync deploy#ip:/var/www/path1 /var/www/path1
my_rsync deploy#ip:/var/www/path2 /var/www/path2
BTW, you should read BashFAQ #50: I'm trying to put a command in a variable, but the complex cases always fail!.

Answer 2

If you want to store the command string into a variable and evaluate it later, you can use eval or an alternative safer technique:
#!/bin/bash
# Store the command into an array
RSYNC=(rsync -avzhe 'ssh -i /path/to/deploy_keys/id_rsa' --delete)
# Run the command
"${RSYNC[#]}" deploy#ip:/var/www/path1 /var/www/path1
Why eval should be avoided

Answer 3

After you assign a string to a variable and then submit it to shell again it is tokenized differently. Consider the following script
VAR="/bin/ls 'Test1 Test2'"
$VAR
It will throw two errors:
/bin/ls: cannot access 'Test1
/bin/ls: cannot access Test2'
You guessed it right, the apostrophes are no longer affecting tokenization. Instead they are treated as normal characters when the commandline arguments are fed to /bin/ls
While eval is rightly considered evil, it is by far the easiest way to get a script running. It stitches all the arguments into one line and applies the tokenizing procedure again.
RSYNC="rsync -avzhe 'ssh -i /path/to/deploy_keys/id_rsa' --delete "
# Files
eval $RSYNC deploy#ip:/var/www/path1 /var/www/path1
eval $RSYNC deploy#ip:/var/www/path2 /var/www/path2