-e escape rule

Samuel Williams space.ship.traveller at gmail.com
Thu Oct 20 09:24:23 UTC 2016


I'm using Ruby's Shellwords module, which generates a string from an
array, suitable for shell evaluation.

Ruby's implementation prefers escaping whitespace with a backslash
rather than quotes. However, this appears to cause some kind of issue
in Rsync when it computes argv from -e option.

Here is an example command generated by some Ruby code:

rsync --archive --stats -e ssh\ -l\ backup\ -i\ /etc/synco/id_rsa\ -o\
ConnectTimeout\\\=60\ -o\ BatchMode\\\=yes --link-dest
../../latest/etc/ /etc/

We can check that something like this is valid:

files% echo foo\ bar\\\=baz
foo bar\=baz             -- what Rsync should be receiving
files% echo foo bar\=baz
foo bar=baz              -- What Rsync should be executing

However this gives me an error

command-line: line 0: Bad configuration option: connecttimeout\\
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: unexplained error (code 255) at io.c(226) [sender=3.1.2]

I think the problem here is the "ConnectTimeout\\\=60", in particular
how the equals symbol is escaped.

I'm looking in the function:

static pid_t do_cmd(char *cmd, char *machine, char *user, char
**remote_argv, int remote_argc,
   int *f_in_p, int *f_out_p)

This function splits based purely on whitespace:

     args[argc++] = t;
     while (*f != ' ' || in_quote) {
         // consume token...

I feel that this function should also handle backslash escapes.

I also checked using strace and it appears that this is the issue, but
I'm open to suggestions/ideas.

Kind regards,

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