Sometime it is necessary to find out if a shell script is being run as root user or not.
When user account created a user ID is assigned to each user. BASH shell stores the user ID in $UID variable. Your effective user ID is stored in $EUID variable. You can
Old way...
You can easily add a simple check at the start of a script:
Check the script is being run by root user
#!/bin/bash # Init FILE="/tmp/out.$$" GREP="/bin/grep" #.... # Make sure only root can run our script if [ "$(id -u)" != "0" ]; then echo "This script must be run as root" 1>&2 exit 1 fi # ...
New way: Using EUID
#!/bin/bash # Init FILE="/tmp/out.$$" GREP="/bin/grep" #.... # Make sure only root can run our script if [[ $EUID -ne 0 ]]; then echo "This script must be run as root" 1>&2 exit 1 fi # ...
Mount /dev/sdb1 only if you are a root
#!/bin/bash if [[ $EUID -ne 0 ]]; then echo "You must be a root user" 2>&1 exit 1 else mount /dev/sdb1 /mnt/disk2 fi
Updated for accuracy and more examples.
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- Last Updated: Jan/6/2008
{ 7 comments… read them below or add one }
Make error messages go to STDERR (Standard Error) like they do in other Unix programs. That is the best way to do things.
if [ "$(id -u)" != "0" ]; then
echo “This script must be run as root” 2>&1
exit 1
fi
Nice suggestion, the post has been updated.
may be it was the wrong place to post this.Please help me,
I would like to send mail for each success login.i tried with this,
and place this in /root/.bashrc
#!/bin/bash
echo `last $i | head -1 | awk ‘{print $1″ “$3″ “$4″ “$5″ “$6″ “$7}’`|while read output;
do
echo $output
ip=$(echo $output | awk ‘{print $2}’ )
on=$(echo $output | awk ‘{print $3″ “$4″ “$5}’ )
at=$(echo $output | awk ‘{print $6′} )
echo “User logged in from $ip on $on at $at”|mail -s “Alert: user logged in to server $(hostname) from $ip” ephrondiana@gmail.com
done
but its sending mail for root login only,i need to send mail for users login also.Please help me…
Hi,
if you want to redirect a message to stderr using echo you have to use “1>&2″ instead of “2>&1″.
For example,
~ >> f(){
> echo “to stdout” 2>&1
> echo “to stderr” 1>&2
> }
~ >> f 2>/dev/null
to stdout #this is printed to stdout
~ >>
bye
I think it’s worth mentioning that $UID & $EUID will not return the desired result if you use sudo to run the script, id -u does however.
@ terry
The script works as expected.
@Diana
You need to put your code into the global .bashrc file, /etc/bashrc. This will become the default .bashrc. Beware though, if you make a user specific bashrc then you need to import the global bashrc