SCP doesn't work when echo in .bashrc?
I have two users in Fedora:
- root (quite obvious!)
My contents of .bashrc of user Wani are:
# .bashrc echo "Hello" # Source global definitions if [ -f /etc/bashrc ]; then . /etc/bashrc fi # User specific aliases and functions
Now after logging into root, I type the following commands:
[root@Dell Wani]# touch try.txt [root@Dell Wani]# service sshd start [root@Dell Wani]# scp try.txt Wani@localhost:~/ Wani@localhost's password: Hello [root@Dell Wani]#
Now I log into Wani, and type:
[Wani@Dell ~]$ cat try.txt cat: try.txt: No such file or directory [Wani@Dell ~]$
Now I again log into root and type the same command with -v:
[root@Dell Wani]# scp -v morph.log Wani@localhost: Executing: program /usr/bin/ssh host localhost, user Wani, command scp -v -t -- . OpenSSH_5.6p1, OpenSSL 1.0.0j-fips 10 May 2012 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Connecting to localhost [127.0.0.1] port 22. debug1: Connection established. debug1: permanently_set_uid: 0/0 debug1: identity file /root/.ssh/id_rsa type -1 debug1: identity file /root/.ssh/id_rsa-cert type -1 debug1: identity file /root/.ssh/id_dsa type -1 debug1: identity file /root/.ssh/id_dsa-cert type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.6 debug1: match: OpenSSH_5.6 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.6 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Host 'localhost' is known and matches the RSA host key. debug1: Found key in /root/.ssh/known_hosts:2 debug1: ssh_rsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi- with-mic,password debug1: Next authentication method: gssapi-keyex debug1: No valid Key exchange context debug1: Next authentication method: gssapi-with-mic debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_0' not found debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_0' not found debug1: Unspecified GSS failure. Minor code may provide more information debug1: Unspecified GSS failure. Minor code may provide more information debug1: Next authentication method: publickey debug1: Trying private key: /root/.ssh/id_rsa debug1: Trying private key: /root/.ssh/id_dsa debug1: Next authentication method: password Wani@localhost's password: debug1: Authentication succeeded (password). Authenticated to localhost ([127.0.0.1]:22). debug1: channel 0: new [client-session] debug1: Requesting firstname.lastname@example.org debug1: Entering interactive session. debug1: Sending environment. debug1: Sending env XMODIFIERS = @im=none debug1: Sending env LANG = en_US.UTF-8 debug1: Sending command: scp -v -t -- . Hello [root@Dell Wani]# debug1: client_input_channel_req: channel 0 rtype exit-status reply 0 debug1: channel 0: free: client-session, nchannels 1 debug1: fd 0 clearing O_NONBLOCK debug1: fd 1 clearing O_NONBLOCK Transferred: sent 1664, received 1976 bytes, in 0.1 seconds Bytes per second: sent 22961.5, received 27266.8 debug1: Exit status 0
(And after I press Enter)
Can anyone please shed some light as to what exactly happened here? Why did the file not get copied to Wani from root?
Using echo in a .bashrc will break scp, as scp expects to see its protocol data over the stdin/stdout channels. See https://bugzilla.redhat.com/show_bug.cgi?id=20527 for more discussion on this issue.
There's a few workarounds available:
- Condition on the 'interactive' flag (e.g. case $- in *i* as suggested by tripleee)
- Use the tty utility to detect an interactive shell (e.g. if tty > /dev/null or if [ -t 0 ])
- Check the value of $SSH_TTY
I suppose you should use whichever one works for you. I don't know what the best (most portable/most reliable) option is, unfortunately.
To add to nneonneo's options, you can also condition with the interactive flag with
if [[ $- =~ "i" ]]
which I think is possibly the clearest way in bash.
This works for me, In .bashrc add first line as:
if [ -z "$PS1" ]; then return fi
The default Ubuntu .bashrc contains the following snippet which already takes care of the problem:
# If not running interactively, don't do anything case $- in *i*) ;; *) return;; esac
In .bashrc, use STDERR as output instead:
echo "# Important Notice" >&2
Update: do not use it! We had an issue recently that a (closed source) tool failed due to an echo to STDERR in .bashrc. The tool (using rcp) expected no output at all, neither on STDOUT nor STDERR. And it stuck when it got the echo. Lesson learned: make separate accounts for humans and for machines (scripts), or just stop tattling via .bashrc.
The most portable way of testing for an interactive shell seems to be:
test -t 0 if [ $? -eq 0 ] then # interactive ; else # non-interactive ; fi
nneonneo's solution worked for me as well. But since my default shell is TCSH, I had to slightly edit the fix as follows (in .tcshrc):
if ( $?SSH_TTY ) then exec /bin/bash endif
Just thought I would share for everyone's benefit.
if [ 0 -eq $(shopt -q login_shell; echo $?) ]; then echo "do something?" fi
If you're on Red Hat Enterprise Linux (RHEL) or variant, drop a script that does the echo, or whatever you want, into /etc/profile.d/