# Scripting with spmenu

This wiki article walks you through how to actually write a script using spmenu.

## Deciding what to write

Before you write anything, you need to have a concept. For this example, we're going to write a script which lists out all Arch packages you could install and then installs it. You could of course do anything you want, though.

## spmenu basics

The core concept of spmenu is to take standard input, list out items separated by a newline character, and output the selected item. For example `printf "1\n2\n3\n" | spmenu --lines 30 --prompt 'Select a number'` will allow you to choose between 1, 2 and 3. The selected item is then output to standard output (stdout)

## Starting off

First, I like to start off my scripts with a `main` function. I would start like this:

```
#!/bin/sh
# My super awesome shell script
# Licensed under the GNU General Public License version 3.0
# See LICENSE file for more information.

main() {
    :
}
```

Now, I know the command to list out all packages in the Arch repositories on your system is `pacman -Sl`. This is going to list out the repository name followed by a space though, and we don't really need to see that. So what I'm going to do is `pacman -Sl | awk '{ print $2 }'`, which gets the second and final column.

```
[speedie@arch ~]$ pacman -Sl | awk '{ print $2 }'
acl
amd-ucode
archlinux-keyring
argon2
attr
audit
autoconf
automake
b43-fwctter
base
...
```

Then what I would do is create another function, and perhaps call it `list_packages()` or something like that, and then I would replace the placeholder `:` with assigning a variable.

```
...

list_packages() {
    pacman -Sl | awk '{ print $2 }'
}

main() {
    sel_item="$(list_packages | spmenu --lines 10 --columns 3 --prompt "Select a package to install:"
}
```

## Checking the output

Alright, now we have the selected item in a variable called `sel_item`. We can easily print what this variable contains by running something like `printf "%s\n" "$sel_item"`. Now we need to use this variable for something. What I would do next is use something like sudo or doas, and enable root without a password. This *could* be insecure, so be careful. For this example though, I'm going to assume you're using sudo, and sudo can execute `pacman -S` without a password.

```
...

main() {
    sel_item="$(list_packages | spmenu --lines 10 --columns 3 --prompt "Select a package to install:")"
    sudo pacman -S --noconfirm "${sel_item}"
}
```

## Notify

Now what I like to do is add a nice litte notification if the package installed successfully. This is optional but I would do it like this:

```
...

main() {
    sel_item="$(list_packages | spmenu --lines 10 --columns 3 --prompt "Select a package to install:")"
    sudo pacman -S --noconfirm "${sel_item}" && notify-send "Installed" "Installed '${sel_item}'." || notify-send "Failed" "Installation of package '${sel_item}' failed."
}
```

Now, finally we need to call the `main()` function, so simply add `main` to the bottom of the script.

The script should look something like this:

```
#!/bin/sh
# My super awesome shell script
# Licensed under the GNU General Public License version 3.0
# See LICENSE file for more information.

list_packages() {
    pacman -Sl | awk '{ print $2 }'
}

main() {
    sel_item="$(list_packages | spmenu --lines 10 --columns 3 --prompt "Select a package to install:")"
    [ -z "${sel_item}" ] && exit # This will exit if we didn't select anything.
    sudo pacman -S --noconfirm "${sel_item}" && notify-send "Installed" "Installed '${sel_item}'." || notify-send "Failed" "Installation of package '${sel_item}' failed."
}

main
```

Now, you could easily expand this to do removal as well, but I'm not going to cover that.