Explaining behaviour of sudo bash "$0" "$@"; Post: 303025441

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Top Forums Shell Programming and Scripting Explaining behaviour of sudo bash "$0" "$@"; Post 303025441 by Corona688 on Friday 2nd of November 2018 11:50:27 AM

11-02-2018

Registered User

For starters, you almost never need to use $?, a normal if-statement will do. Written this way, you can kind of see the logic. "If not sudo, then ..."

Not sure if it's really a simplification but I'd add >&2, the traditional place for error messages. That way if someone uses this in a stream they can direct data output and error output separately.

You should have an exit after exec, in case the exec fails for whatever reason (i.e. path problems or something).

Then I'd label the section which is always intended to run as root.

Code:

#!/bin/bash

# If we can't run sudo without a password, complain and exit
if ! sudo -n true 2> /dev/null
then
       echo "please run as root" >&2
       echo "haha you have not power here" >&2
       echo "You need to enter password" >&2
       
       # Not sure if you want this or not?  Exits after printing error/warning
       exit 1
fi

# If EUID isn't zero, replace and re-run this script as root using sudo.
if [ "$EUID" -ne 0 ]
then
        exec sudo bash "$0" "$@"
        echo "exec failed" >&2
        exit 1
fi

#########################################
####### The below section always runs as root #########
#########################################

declare commandOutput=$(apt-add-repository multiverse);
if echo "$commandOutput" | grep -q "distribution component is already enabled"; then 
  echo "multiverse repository is already enabled" >&2
fi

The "replace and re-run" bit comes down to how exec really works: It causes the running program to replace itself with what you ask. Whether it succeeds or fails, after an

The >&2's make more likely that these messages get printed to the terminal, where these messages usually belong.

More could probably be done with apt-get, like checking its return value rather than just assuming it operates correctly.

Last edited by Corona688; 11-02-2018 at 12:56 PM..

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NAME

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       used to set up an environment more controlled than the standard shell.  It behaves identically to bash with the exception that the  follow-
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