How to pipe a remote file to stdout over scp or sftp?

Question

Using ssh, it is easy to print the contents of a file using

ssh host 'cat file.txt'

When ssh is disabled, and only SFTP is enabled, running the previous command gives the following error:

This service allows sftp connections only.

To work-around this issue, I could create a temporary file using scp or sshfs (as shown below), but that looks really ugly. What is the proper way to print the contents of a remote file when SSH is disabled?

mkdir tmpdir
sshfs host: tmpdir
cat tmpdir/file.txt
fusermount -u tmpdir

# This does not work! scp -v host:file.txt . shows
# "Sink: This service allows sftp connections only."
scp host:file.txt .
cat file.txt
rm file.txt

Kenster · Answer 1 · 2018-03-10T18:16:47.300

39

For people who can run scp, you can do this:

scp remotehost:/path/to/remote/file /dev/stdout

edited Mar 10 '18 at 18:16

answered Jul 29 '14 at 12:32

Kenster

3,025
2
13
19

Neither method works. The first one is equivalent to the one-liner `sftp username@hostname:/path/to/file.txt /dev/stdout` and results in "Couldn't write to "/dev/stdout": Illegal seek". The second command fails, and shows the error that is shown at the bottom of my question. – Rob W Jul 29 '14 at 14:14
The SFTP form works fine for me. It may depend on what version of the ssh software you're using. Regarding scp, I did say "if scp works". You established in your question that the server was not permitting you to perform scp, so naturally the scp command would fail for you. – Kenster Jul 29 '14 at 17:06
`ssh -V` gives `OpenSSH_6.6.1p1, OpenSSL 1.0.1h 5 Jun 2014`. scp fails because it uses ssh under the hood, and ssh is disabled (as a security measure, see e.g. http://serverfault.com/questions/354615/allow-sftp-but-disallow-ssh) – Rob W Jul 29 '14 at 17:13

score 19 · Accepted Answer · edited Jul 28 '14 at 22:36

19

Curl can display the file the same way cat would. No need to delete the file since it simply displayed the output unless you tell it to do otherwise.

curl -u username:password sftp://hostname/path/to/file.txt

If you use public key authentication:

curl -u username: --key ~/.ssh/id_rsa --pubkey sftp://hostname/path/to/file.txt

If you use the default locations, then --key and --pubkey can be omitted:

curl -u username: sftp://hostname/path/to/file.txt

The user name can also be a part of the URL, so the final result looks very close to the ssh command:

curl sftp://username@hostname/path/to/file.txt

edited Jul 28 '14 at 22:36

Rob W

898
1
8
17

answered Jul 28 '14 at 18:30

brwtx

391
2
4

Thanks, exactly what I was looking for! I have edited your answer to expand on public-key authentication, it turns out that the syntax is very similar to the ssh/sshfs syntax. If the curl command fails with "curl: (51) SSL peer certificate or SSH remote key was not OK", just add the `-k` flag (`--insecure`). – Rob W Jul 28 '14 at 21:46

Anton Duzenko · Answer 3 · 2023-03-03T11:30:51.503

0

On Ubuntu I was able to open the remote directory in Files GUI, then "Open in Local Terminal"

At this point I was navigated to a funny path looking like /run/user/1000/gvfs/sftp:host=qweqwe.synology.me/Prod_Backup/DB

From there I could read and pipe files similar to local file systems.

Unfortunately the speed was not adequate for my needs (~200 KB/s).

edited Mar 03 '23 at 11:30

answered Mar 03 '23 at 11:20

Anton Duzenko

101
3

score 0 · Answer 4 · answered Mar 03 '23 at 11:54

0

With lftp:

lftp -e 'set cmd:show-status 0; cat -b remote/file' sftp://user@host < /dev/null

(</dev/null to force it to be non-interactive).

answered Mar 03 '23 at 11:54

Stéphane Chazelas

522,931
91
1,010
1,501

How to pipe a remote file to stdout over scp or sftp?

4 Answers4