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Top Forums Shell Programming and Scripting unwanted control character in the input Post 302365514 by jeff_cen on Tuesday 27th of October 2009 09:27:31 AM
Old 10-27-2009
unwanted control character in the input

Hi Shell Scripting Experts,

I have a shell script running daily on a remote machine through ssh. To avoid the trouble of restarting the script when ssh disconnects, I use screen (a unix tool) and run the script within a screen session.

What this script does is to ask the user to input y or n daily and does some file appending based on the input. The following is the script

Code:
echo -n "DO YOU WANT TO APPEND FILE(y/n)? "
read qq

if [ $qq = "y" ]  
then
  echo "appending..."

else
  echo "quitting..." 
fi

However, one strange problem is that occasionally an unwanted character is put before a user's input. The following the full screen output by running sh -x myscript.sh. Notice that the user input a single character y but \020y was the one taken by the session. This problem does not occur always. I don't know whether it has to with the screen tool or something else.

Code:
+ echo -n 'DO YOU WANT TO APPEND FILE(y/n)? ' 
DO YOU WANT TO APPEND PREDS(y/n)? + read qq 
y 
+ '[' $'\020y' = y ']' 
+ echo quitting... 
quitting...

Any suggestions is highly appreciated.

thanks

Jeff

Last edited by Franklin52; 10-27-2009 at 10:29 AM.. Reason: Please use code tags!
 

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SSH-COPY-ID(1)						      General Commands Manual						    SSH-COPY-ID(1)

NAME
ssh-copy-id - install your public key in a remote machine's authorized_keys SYNOPSIS
ssh-copy-id [-i [identity_file]] [user@]machine DESCRIPTION
ssh-copy-id is a script that uses ssh to log into a remote machine and append the indicated identity file to that machine's ~/.ssh/autho- rized_keys file. If the -i option is given then the identity file (defaults to ~/.ssh/id_rsa.pub) is used, regardless of whether there are any keys in your ssh-agent. Otherwise, if this: ssh-add -L provides any output, it uses that in preference to the identity file. If the -i option is used, or the ssh-add produced no output, then it uses the contents of the identity file. Once it has one or more fin- gerprints (by whatever means) it uses ssh to append them to ~/.ssh/authorized_keys on the remote machine (creating the file, and directory, if necessary.) NOTES
This program does not modify the permissions of any pre-existing files or directories. Therefore, if the remote sshd has StrictModes set in its configuration, then the user's home, ~/.ssh folder, and ~/.ssh/authorized_keys file may need to have group writability disabled manu- ally, e.g. via chmod go-w ~ ~/.ssh ~/.ssh/authorized_keys on the remote machine. SEE ALSO
ssh(1), ssh-agent(1), sshd(8) OpenSSH 14 November 1999 SSH-COPY-ID(1)
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