rsync - Apr 2008 - scripting rsync ssh port issue

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On Fri 04 Apr 2008, Sterling Windmill wrote:
> I am modifying a bash script of mine to issue an rsync to a remote host
with a non-standard ssh port.
> 
> Unfortunately, no combination of "bashisms" seems to make it work
properly.
> 
> Code snippet:
> 
> ...
> 
> RSYNC_OPTIONS="-aH --delete --numeric-ids -e \'ssh -p
2292\'"
> RSYNC="ionice -c3 rsync $RSYNC_OPTIONS"
Nested quotations usually do something else than you'd expect...
> $SOURCE=/some/dir
> $DEST=root@10.2.10.1:/some/dir
Are you sure about the above lines? I'd lose the $ in the 1st column.
(Or was that your shell prompt...)

> $RSYNC --progress  "$SOURCE" "$DST"
That will probably present the arguments to rsync differently then
expected. A simple test:

$ cat showargs.sh
#!/bin/sh

for i; do
    echo "ARG: $i"
done


$ RSYNC_OPTIONS="-aH --delete --numeric-ids -e \'ssh -p
2292\'"
$ RSYNC="ionice -c3 rsync $RSYNC_OPTIONS"
$ SOURCE=/some/dir
$ DEST=root@10.2.10.1:/some/dir
$ ./showargs.sh $RSYNC --progress  "$SOURCE" "$DST"
ARG: ionice
ARG: -c3
ARG: rsync
ARG: -aH
ARG: --delete
ARG: --numeric-ids
ARG: -e
ARG: \'ssh
ARG: -p
ARG: 2292\'
ARG: --progress
ARG: /some/dir
ARG: 

(With $DEST instead of $DST it shows root@10.2.10.1:/some/dir as the
last ARG, instead of the empty one now.)

I wish you much pleasure in trying to solve this in this way :-)
I'd create a ssh-2292 commmand that looks like:

#!/bin/sh
exec /usr/bin/ssh -p 2292 "$@"

and pass that to the -e option.

Alternatively you could create an entry for that host in ~/.ssh/config
and put the port in there.


Paul Slootman

Paul has addressed the errant dollar signs, the misspelled $DST, and two
possible workarounds for the quoting issue, but I would like to explain
the quoting issue a bit further.

On Fri, 2008-04-04 at 11:23 -0400, Sterling Windmill
wrote:
> RSYNC_OPTIONS="-aH --delete --numeric-ids -e \'ssh -p
2292\'"
> RSYNC="ionice -c3 rsync $RSYNC_OPTIONS"
>  
> $SOURCE=/some/dir
> $DEST=root@10.2.10.1:/some/dir
>  
> $RSYNC --progress  "$SOURCE" "$DST"
> Missing trailing-' in remote-shell command.
> rsync error: syntax or usage error (code 1) at main.c(364)
> [sender=3.0.0]
>  
> If I paste the command directly into a command line, the command works
> properly.
First, get rid of the backslashes in $RSYNC_OPTIONS because they are
being taken literally; single quotes need no escaping inside double
quotes.

Second, when bash expands a variable like $RSYNC, it takes quotes in the
variable's value literally; they do not protect spaces in the expanded
value from word splitting.  Thus, bash is splitting your -e value into
three pieces, the first and last of which contain unmatched single
quotes, hence the rsync error.

You could fix this by using "eval" instead of word-splitting
expansion,
but that would be fragile with respect to shell metacharacters in the
arguments to be passed to rsync.  Alternatively...
> I've also tried taking the advice mentioned here and using an array
> instead of a variable, but to no avail:
>  
> http://wooledge.org:8000/BashFAQ/050
Arrays are generally the best solution, but it takes some care to use
them correctly.  Here's your script rewritten to use arrays:

---

RSYNC_OPTIONS=(-aH --delete --numeric-ids -e 'ssh -p 2292')
RSYNC=(ionice -c3 rsync "${RSYNC_OPTIONS[@]}")

SOURCE=/some/dir
DEST=root@10.2.10.1:/some/dir

: "${RSYNC[@]}" --progress "$SOURCE" "$DEST"

---

Matt
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