为什么scp会给出这个奇怪的输出？

Question

我有两台计算机(legend和telos)运行Debian11。出于某种原因，scp命令失败了，出现了一条奇怪的错误消息。

这是输出：

jj@telos:~$ scp test.txt legend.local:
   __                        __

如果我用相反的方法尝试，下划线和空格的数量会有所不同：

jj@legend:~$ scp telos.local:test.txt .
 ______    __

下面是带有-v参数的输出：

jj@telos:~$ scp -v test.txt legend.local:
Executing: program /usr/bin/ssh host legend.local, user (unspecified), command scp -v -t .
OpenSSH_8.4p1 Debian-3, OpenSSL 1.1.1i  8 Dec 2020
debug1: Reading configuration data /home/jj/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: Connecting to legend.local [192.168.178.31] port 22.
debug1: Connection established.
debug1: identity file /home/jj/.ssh/id_rsa type 0
debug1: identity file /home/jj/.ssh/id_rsa-cert type -1
debug1: identity file /home/jj/.ssh/id_dsa type -1
debug1: identity file /home/jj/.ssh/id_dsa-cert type -1
debug1: identity file /home/jj/.ssh/id_ecdsa type -1
debug1: identity file /home/jj/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/jj/.ssh/id_ecdsa_sk type -1
debug1: identity file /home/jj/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /home/jj/.ssh/id_ed25519 type -1
debug1: identity file /home/jj/.ssh/id_ed25519-cert type -1
debug1: identity file /home/jj/.ssh/id_ed25519_sk type -1
debug1: identity file /home/jj/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /home/jj/.ssh/id_xmss type -1
debug1: identity file /home/jj/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.4p1 Debian-3
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.4p1 Debian-3
debug1: match: OpenSSH_8.4p1 Debian-3 pat OpenSSH* compat 0x04000000
debug1: Authenticating to legend.local:22 as 'jj'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC:  compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC:  compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:IUzxufu5zBuFsNU/SyjfpFr7U4bvqfsXVdP/6CTstUw
debug1: Host 'legend.local' is known and matches the ECDSA host key.
debug1: Found key in /home/jj/.ssh/known_hosts:44
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: /home/jj/.ssh/id_rsa RSA SHA256:FND4H+2/T2jRUqT9+aNHocv5Mg7yjfS3WtQGaC9aQR8
debug1: Will attempt key: /home/jj/.ssh/id_dsa 
debug1: Will attempt key: /home/jj/.ssh/id_ecdsa 
debug1: Will attempt key: /home/jj/.ssh/id_ecdsa_sk 
debug1: Will attempt key: /home/jj/.ssh/id_ed25519 
debug1: Will attempt key: /home/jj/.ssh/id_ed25519_sk 
debug1: Will attempt key: /home/jj/.ssh/id_xmss 
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /home/jj/.ssh/id_rsa RSA SHA256:FND4H+2/T2jRUqT9+aNHocv5Mg7yjfS3WtQGaC9aQR8
debug1: Server accepts key: /home/jj/.ssh/id_rsa RSA SHA256:FND4H+2/T2jRUqT9+aNHocv5Mg7yjfS3WtQGaC9aQR8
debug1: Authentication succeeded (publickey).
Authenticated to legend.local ([192.168.178.31]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Remote: /home/jj/.ssh/authorized_keys:1: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: /home/jj/.ssh/authorized_keys:1: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Sending environment.
debug1: Sending env LANG = en_GB.UTF-8
debug1: Sending command: scp -v -t .
   __                        __
debug1: client_input_channel_req: channel 0 rtype exit-signal reply 0
debug1: channel 0: free: client-session, nchannels 1
debug1: fd 0 clearing O_NONBLOCK
Transferred: sent 2920, received 3300 bytes, in 0.5 seconds
Bytes per second: sent 6164.1, received 6966.2
debug1: Exit status -1
jj@telos:~$ 

当然，______ __是我收到过的最奇怪的错误信息。怎么啦？

Answer 1

问题是两方面的。首先，在我的~/.profile中有以下声明：

. ~/.bashrc

其次，我的~/.bashrc中有以下声明：

name=$(hostname)
figlet -f smslant ${name^}

这将在登录到legend时产生以下输出：

   __                        __
  / /  ___ ___ ____ ___  ___/ /
 / /__/ -_) _ `/ -_) _ \/ _  / 
/____/\__/\_, /\__/_//_/\_,_/  
         /___/                 

注意到上面的那一行了吗？这就是scp所输出的台词！我通过在~/.bashrc中加上以下内容来解决这个问题：

# If not running interactively, don't do anything
case $- in
    *i*) ;;
      *) return;;
esac