Why the remote ls from here doc from ssh does not work within a $()?

Question

I am trying to count the number of files in a remote directory.
I have the following code:

ssh server.com<<RUNTHIS  
 FILE_COUNT=$(ls -AU /foo/bar/test_dir) 
 echo "$FILE_COUNT" > ~/file_count.txt   
RUNTHIS

When I run this I get: ls: /foo/bar/test_dir No such file or directory
But the directory is there. If I do ls /foo/bar/test_dir directly to the server it lists the directory.
Also the following works and saves the contents to the file:

ssh server.com<<RUNTHIS  
 ls -AU /foo/bar/test_dir > ~/file_count.txt
RUNTHIS

What is wrong in the first snippet?

Rastapopoulos · Answer 1 · 2017-10-19T16:04:46.280

0

It doesn't work because bash will do parameter expansion and command substitution in the heredoc. Try with single quotes around RUNTHIS to protect it.

ssh server.com<<'RUNTHIS' 
 FILE_COUNT=$(ls -AU /foo/bar/test_dir) 
 echo "$FILE_COUNT" > ~/file_count.txt   
RUNTHIS

edited Oct 19 '17 at 16:04

answered Oct 19 '17 at 15:00

Rastapopoulos

1,669

A less weird way to do this would be ssh server.com "ls -AU" > ~/file_count.txt (If I recall how to ssh correctly) – SIGSTACKFAULT Oct 19 '17 at 15:07
That won't work for me. I have other commands as part of that block that break if I add the single quote. – Jim Oct 19 '17 at 15:13
@Blacksilver: that doesn't do the same thing though, does it. (It writes the file locally and not remotely). – Rastapopoulos Oct 19 '17 at 16:08
@Jim: Where does it break if you use single quotes? Could you give an example? – Rastapopoulos Oct 19 '17 at 16:10
oh, do you want to write to a remote file? ssh server.com "ls -AU > ~/file_count.txt" – SIGSTACKFAULT Oct 19 '17 at 16:11
Yes, that does work for the example (changing the argument of ls). :) – Rastapopoulos Oct 19 '17 at 16:21
@Rastapopoulos: It is mentioned even in the docs. I need all my commands in the snippet to run and some are quoted etc – Jim Oct 19 '17 at 16:34
What is mentioned? I don't see what the problem in the case of your example... – Rastapopoulos Oct 19 '17 at 16:54

score 0 · Answer 2 · answered Oct 19 '17 at 17:44

0

The problem is your $(ls) expands locally, rather than remotely.

Try this...

ssh -2 -4 -i $key root@$ip -- 'ls -AU /foo/bar/test_dir | wc -l > ~/file_count.txt'

answered Oct 19 '17 at 17:44

David Favor

423

Why the remote ls from here doc from ssh does not work within a $()?

2 Answers2