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Old 04-10-2017, 12:58 PM   #1
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concatenate username, password and program object

before moving to Linux in the AIX world, we would run the cat command to pass the username and password to the program object like this:


cat $USR $PASS | $file > $outfile 2>&1

Now that we have moved to Linux, this no longer works. The user is read in by the program to be userpassword and the password read in by the program is blank. I cannot find a way to force each variable to be a separate parameter, one username and one password.

How can I fix this?
Old 04-10-2017, 01:14 PM   #2
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Hi jill buck and welcome to LQ.

Using Bash, you can enable verbose output by issuing the "set -xv" command, and you can do that at the start of a script, or in the command line. To disable this you issue the "set +xv" command. Note you need only disable in the command line. A script will start a new process, which will complete and the setting will not be retained. This will allow you to debug your lines.

You create a new file using the I/O redirection argument: >
You can append to a file using the I/O redirection argument: >>

This is not AIX, nor are the file structures for username and password saved anywhere. Are these files which you are creating, or on AIX were you reading system files? In Linux, the passwords are not stored in plain text, so any attempt to echo them will not work. If you have created these files, then that will work, however it is dangerous to do so.

I haven't tested, but I suspect that the cat will not like two file names together, otherwise all seems fine. So you may have to do two cat function calls, and thus one creates the file and the second one appends to it.

Enabling the verbose output will give you a better idea where the problem with your script exactly is.

You may not be using the Bash shell, but it is one of the most common ones. Issue the command:
$ echo $0
to get an output of which shell you are using.

Please also reply to tell us if this is a script, or a series of command line arguments.

Last edited by rtmistler; 04-10-2017 at 01:16 PM.
Old 04-10-2017, 01:26 PM   #3
Ser Olmy
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Originally Posted by jillbuck View Post
cat $USR $PASS | $file > $outfile 2>&1
This basically says "send the contents of the files $USR and $PASS to stdout, which should then be redirected to the input of the program $file". That will work in one scenario and one scenario only:
  1. $file expects the user to type in a username and a password,
  2. the combined contents of $USR and $PASS matches exactly what $file expects to see, and
  3. the application $file accepts input redirection
I suspect (3) might be the issue. Many GNU applications (like passwd) are explicitly made not to accept passwords from stdin. If you want to automate a login process, or really any interactive command line operation, you should take a look at expect.

Last edited by Ser Olmy; 04-10-2017 at 01:32 PM.


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