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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LEARN ABOUT DEBIAN

viewsudo

VIEW-OS(1)						      General Commands Manual							VIEW-OS(1)

NAME

       viewsudo - execute a command as another (virtual) user

SYNOPSIS

       viewsudo [-g groupname|#gid] [-u username|#uid] command

DESCRIPTION

       viewsudo allows a user to execute a command as the superuser or
	      another user in View-OS.

OPTIONS

       viewsudo accepts the following command line options:

       -g group
	   Normally,  viewsudo	sets the primary group to root.  The -g option causes sudo to run the specified command with the primary group set
	   to group.  To specify a gid instead of a group name, use #gid.  When running commands as a gid, many shells require	that  the  '#'	be
	   escaped  with  a  backslash	('[u2019]).   If  no -u option is specified, the command will be run as the invoking user (not root).	In
	   either case, the primary group will be set to group.

       -u user
	   The -u option causes viewsudo to run the specified command as a user other than root.  To specify a uid instead of  a  user	name,  use
	   #uid.  When running commands as a uid, many shells require that the '#' be escaped with a backslash ('[u2019]).

RETURN VALUES

       Upon successful execution of a program, the exit status from viewsudo will simply be the exit status of the program that was executed.

SEE ALSO

       viewsu(1), sudo(1), linux.defs(5)

AUTHORS

       View-OS is a project of the Computer Science Department, University of Bologna. Project Leader: Renzo Davoli.
       <http://www.sourceforge.net/projects/view-os>

       Howto's and further information can be found on the project wiki <wiki.virtualsquare.org>.

NOTE

       Most part of the text is taken from sudo(1).

VIEW-OS: a process with a view					  August 8, 2009							VIEW-OS(1)