Solved How to find out if script is being run as root

[iSh0w]

Hey guys,

Not to compare FreeBSD to Linux but in Linux one can use the following code in a .sh file to check if it is being run as root, is there a similar solution for FreeBSD i.e. to check if FreeBSD is running the script as root.

#!/bin/sh
# 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

/iSh0w

 

[kpa]

You can use id -u in place of $EUID.

id(1)

 

[iSh0w]

Please pardon my ignorance, I keep getting

[:missing]

with the following code:

#!/bin/sh
# Init
# Make sure only root can run our script
idusr=$(id -u);
rootusr=0;
if [ x${idusr} != x${rootusr}]; then
   echo "This script must be run as root"
   exit;
fi

Probably my if-else syntax/statement is flawed

/iSh0w

 

[tobik@]

You have [ x${idusr} != x${rootusr}]; but you need [ x${idusr} != x${rootusr} ]; (missing a space before ])

You could also write it like this:

if [ $(id -u) -ne 0 ]; then
   echo "This script must be run as root"
   exit;
fi

id -u should work under Linux too.

 

[kpa]

Ahem, stop with the prefix silliness that is so common in Linux shell scripting. Use proper quoting so that you don't have to use the x prefix:

if [ "${idusr}" != "${rootusr}" ]; then

The double quotes will guarantee that both sides of the comparison are always defined as empty strings at least.

The reason why you need a space before the ] is that the ] is actually the last argument for test(1) that you're now writing as [ and test(1) is complaining that it can't find the terminating ].

 

[usdmatt]

If you have similar statements in other places of the script where you need to exit on error, I find an error routine comes in handy:

[ `id -u` -ne 0 ] && _err "You must be root to run this"

_err(){
    # ... any additional error handling/recording you want ...
    echo "${0}: $1" >&2
    exit 1
}

Also, when trying to fast track learning shell, I found the scripts in /etc/rc.d, written by devs that know what they're doing, highly useful. There's all sorts of clever snippets of code in there.

 

[iSh0w]

If you have similar statements in other places of the script where you need to exit on error, I find an error routine comes in handy:

[ `id -u` -ne 0 ] && _err "You must be root to run this"

_err(){
    # ... any additional error handling/recording you want ...
    echo "${0}: $1" >&2
    exit 1
}

Also, when trying to fast track learning shell, I found the scripts in /etc/rc.d, written by devs that know what they're doing, highly useful. There's all sorts of clever snippets of code in there.

Thanks a bunch guys!

/iSh0w

 

[acheron]

$uid should do the trick

 

[wblock@]

$uid should do the trick

What he said. Or $euid. Do those depend on the shell, or is there some other reason people did not mention them?

 

[acheron]

Looks like it depends on the shell: it doesn't work with sh or bash

 

[junovitch@]

devel/checkbashisms can be helpful with this. Keep it in mind in the future.

 % checkbashisms test.sh
possible bashism in test.sh line 7 ($EUID should be "$(id -u)"):
if [[ $EUID -ne 0 ]]; then
possible bashism in test.sh line 7 (alternative test command ([[ foo ]] should be [ foo ])):
if [[ $EUID -ne 0 ]]; then

 

[fnoyanisi]

Just an idea about an possible "more portable" way....

you can run ps(1) and grep(1) the output to find your script ($0) along with UID.
Below runs on SunOS 5.10 (aka Solaris 10) - I don't have access to a FreeBSD machine now. You need to change the ps(1) command and the column to be displayed (i.e. $3 in the code below) by awk(1) in the FreeBSD version.

#!/bin/sh
mycmd=`basename $0`
myuid=`ps -l | grep $mycmd | awk '{ print $3}'`
echo $myuid

Instead of backticks, you may want to use $(...) notation, which superseded the `...` form of command substitution. See this link for more details.

 

[scottro]

junovitch@ thank you, I hadn't known about devel/checkbashims. I remember, years ago, doing some bashism on an AIX box, and being annoyed before I realized the problem.

As for $(...) keep in mind it won't work on csh, where backticks will. So if you wanted copy something as root with the date, you'd have to do cp somefile ~scottro/somefile-`date +%F`. Not relevant to this situation, but just something to remember if you're working in csh.