SCP doesn't work when echo in .bashrc?

Question

I have two users in Fedora:

1. Wani
2. 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 [email protected] 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)

[root@Dell Wani]#  

Can anyone please shed some light as to what exactly happened here? Why did the file not get copied to Wani from root?

Answer 1

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.

Answer 2

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.