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Top Forums Shell Programming and Scripting Change existing variable value only user enters non-empty string. Post 302422547 by kchinnam on Tuesday 18th of May 2010 05:31:02 PM
Old 05-18-2010
Change existing variable value only user enters non-empty string.

I haven't checked any installation script to see how this is done..

But I could not even do following simple task.

How do I Change existing variable value only when user enteres non-empty string. ?


Code:
 
#!/usr/bin/ksh
uid="scott"
# Assign new value user enters to uid, else leave it alone.
 
echo "Press Enter to select existing value \r\n"
echo "uid[${uid}]: \c"; read resp;
 
# if user changes uid to something, then only change original value.
if [ ! -n "${resp}" ]; then
  echo "${resp}" | od -bcx
  # I do not want to capture "Enter" or space characters into this.
  uid=${resp}
fi
echo "uid --> ${uid}"


I want to see output with "uid --> scott" in this case.

Code:
 
$> test.sh   
Press Enter to select existing value 
uid[scott]: 
0000000 012
          \n
            0a00
0000001
uid -->

 

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SETUID(1)						      General Commands Manual							 SETUID(1)

NAME
setuid - run a command with a different uid. SYNOPSIS
setuid username|uid command [ args ] DESCRIPTION
Setuid changes user id, then executes the specified command. Unlike some versions of su(1), this program doesn't ever ask for a password when executed with effective uid=root. This program doesn't change the environment; it only changes the uid and then uses execvp() to find the command in the path, and execute it. (If the command is a script, execvp() passes the command name to /bin/sh for processing.) For example, setuid some_user $SHELL can be used to start a shell running as another user. Setuid is useful inside scripts that are being run by a setuid-root user -- such as a script invoked with super, so that the script can execute some commands using the uid of the original user, instead of root. This allows unsafe commands (such as editors and pagers) to be used in a non-root mode inside a super script. For example, an operator with permission to modify a certain protected_file could use a super command that simply does: cp protected_file temp_file setuid $ORIG_USER ${EDITOR:-/bin/vi} temp_file cp temp_file protected_file (Note: don't use this example directly. If the temp_file can somehow be replaced by another user, as might be the case if it's kept in a temporary directory, there will be a race condition in the time between editing the temporary file and copying it back to the protected file.) AUTHOR
Will Deich local SETUID(1)
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