Rsync command variable, bash script

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.

Related question with a more descriptive title: http://stackoverflow.com/q/5730881/1328439 — Dmitri Chubarov, Jul 08 '15 at 11:38

score 3 · Accepted Answer · answered Jul 08 '15 at 17:06

3

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!.

answered Jul 08 '15 at 17:06

Gordon Davisson

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IMHO this is the most beautiful in terms of invocation, so I rewrote the code to shell function style. – Aron Novak Jul 09 '15 at 07:29

score 2 · Answer 2 · edited May 23 '17 at 11:43

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}

edited May 23 '17 at 11:43

Community

1
1

answered Jul 08 '15 at 10:57

Eugeniu Rosca

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14
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I modified the script quickly, but it still throws the same error unfortunately. – Aron Novak Jul 08 '15 at 11:03
1

@AronNovak add double quotes around `"${RSYNC[@]}"` and it should work. – Dmitri Chubarov Jul 08 '15 at 11:24

Dmitri Chubarov · Answer 3 · 2015-07-08T11:18:07.737

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

Rsync command variable, bash script

3 Answers3