Bash scripts requiring sudo password

42
votes

I'm creating a Bash installer script which compiles and installs some libraries for both OSX and Linux. Because some commands in my script ("make install", "apt-get install", "port install", etc) require sudo, I need the user to supply the password.

Currently the user gets asked for the password whenever the first sudo command is about to execute, but because this is often after a compile stage, there is always some time between starting the script and having to enter the password.

I would like to put the password entry + check at the beginning of the script. Also I am curious if this is really an ok way of installing system libraries.

Alternatively I could install the libraries in a local sandbox location which doesn't require sudo, but then I'll have to tell apt-get and macports where to install their libraries other then the default /usr/local/ and /opt/local, and I'm not sure how to do that nor if that's a clever idea at all.

4
bashsudo

4 Answers

78
votes

To get the password, just put sudo echo "Thanks." at the start of the script.

But I would prefer this solution:

if [[ $UID != 0 ]]; then
    echo "Please run this script with sudo:"
    echo "sudo $0 $*"
    exit 1
fi
5
votes

For those who don't want to elevate the entire script (to limit risks by only using sudo within the script where needed) the first part of the accepted answer sudo echo "Thanks" works but won't respond to sudo password failure by exiting the script. To accomplish this, scripts that include sudo commands and want to ensure sudo access before it's used could start with

if [[ ! $(sudo echo 0) ]]; then exit; fi

The caveat is that you are relying on the existence of a sudoers timeout that will last the duration of your script to suppress the rest of the prompts.

1
votes

Another way to go about it :

function checkSudo() {
    if ((EUID != 0)); then
        echo "Granting root privileges for script ( $SCRIPT_NAME )"
        if [[ -t 1 ]]; then
            sudo "$0" "$@"
        else
            exec 1>output_file
            gksu "$0" "$@"
        fi
        exit
    fi
}
1
votes

Maybe a bit easier to read:

[ $(whoami) == "root" ] || exit