Bash Scripting Question

[cdgary]

I'm a newbie to bash shell scripting and I wanted to know if you create a bash script to perform a yum operation such as yum groupinstall, the system will eventually prompt you for a y or n response when running this from the command line. How do you deal with that in your script or any other situation where you have to respond to something the system will ask before moving forward, like a password or yes/no after performing a command?

Thanks

[coffee412]

Your actual yum command line would be:

yum -y install blah.blah.

Then you dont have to mess with answering YES to yum.

Have a great one!

---Edit---
Didnt see the last part of your question. I think alot of commands have a switch to bypass the question. So, WHen running a command in a script you should investigate the command and first see if it offers something along the lines of the -y like in yum. Thats the easiest.

[sea]

To check if an application is installed with yum, you might modify this script:

    askyum="Ask yum if awesome is installed..."
    printf "Searching..." "awesome repo"
    printf "$askyum" " "
    tpp=$(yum list installed awesome)
    echo $tpp | grep "Installed Packages awesome" && test ! "" = "$tpp" && scecho "$askyum" "$SUCCESS" || scecho "$askyum" "$FAILURE"

Or to install a missing repo:

# |
# | Check if repo is installed 
    repoInstalled=$(ls /etc/yum.repos.d/*awesome*)
    if [[  "" = "$repoInstalled" ]]
        then    if ask "The awesome repo was not found, get it now?" ; then
	                cd /etc/yum.repos.d
                    su -c "wget -nc http://repos.fedorapeople.org/repos/thm/awesome/fedora-awesome.repo"
                else
                    scecho "Sorry, but without the repo you cant install awesome." " "
                    scecho "Exiting now..." " "
                fi
      fi

G'night

[weitjong]

If I understand OP correctly, "yum" is mentioned only as an example. The general way to provide user input to another program/script within your bash script is by redirecting the stdin (<), or by using a HEREDOC (<<), or by piping (|). For the latter, if the respond is a fixed answer like always 'y' or 'n' then you can use piping in tandem with "yes" command, e.g. "yes |other-program" or "yes n |other-program".

[jamielinux]

Originally Posted by sea

    tpp=$(yum list installed awesome)
    echo $tpp | grep "Installed Packages awesome" && test ! "" = "$tpp" && scecho "$askyum" "$SUCCESS" || scecho "$askyum" "$FAILURE"

Really no need for echo/grep/test. Yum returns non-zero value if the package is not found.

[RupertPupkin]

Originally Posted by cdgary

How do you deal with that in your script or any other situation where you have to respond to something the system will ask before moving forward, like a password or yes/no after performing a command?

As weitjong mentioned there are several ways to do this, but my favorite is to use Expect, which is in the Fedora repos. Basically, the way Expect works is you write a script that automates answers for what you "expect" a program to ask you. In fact, you don't even have to write the script yourself; Expect includes a utility called autoexpect which can create it for you from an example session that you go through. It's very simple to use.

One thing you should be careful about, though, is storing plain-text passwords in scripts. That's usually a big security no-no. There are ways to avoid that by using encryption or other methods.

[marriedto51]

+1 for expect.

In fact you will find in some cases that trying to pipe or redirect stdin for an interactive process will not work. (One example is using telnet to retrieve mail from a POP3 server -- which you can achieve using expect instead.)