[SOLVED] How do I send the end of file character to an ssh connection programmatically

Issue

I would like to simulate this shell session:

$ ssh remotehost
[remote] $ cat > /tmp/test.txt
testing
newline
^D[remote] $ echo another cmd
another cmd
[remote] $ ^D

which will create a new file /tmp/test.txt with the content "testing\nnewline\n", then run another command and terminate the ssh session.

I know that the ascii value for the EOT (end of transmission character) is 0x04. So I thought I could emulate this by running:

$ echo "cat > /tmp/test.txt\ntesting\nnewline\n\x04echo another command\n" | ssh -tt remotehost

This seems to work in that it properly sends the commands, but it gets stuck when the end of file character should end the cat command. What am I doing wrong?

Solution

Thank you @dave_tompson_085. Your comment made me realize I should check timings, and use printf. The following command works:

(printf 'cat > /tmp/test.txt\n'; 
 sleep 2; 
 printf 'testing\nnewline\n\x04'; 
 sleep 1; 
 printf 'echo another command\n\x04') | ssh -tt ...

An alternative solution is to use a here doc in the call to the cat command.

Answered By - Jason Eveleth

Answer Checked By - Marie Seifert (WPSolving Admin)