TW Blog :: Archives for June 2005

Verify Sudo in Script Execution

Relates to Apache and UNIX, OSX

Earlier I was setting up a couple of shell scripts to allow me to quickly switch between PHP versions on the Apache web server and enable/disable my unit testing environment in OS X. Along the lines of:

apachectl stop
httpd -f /usr/local/php5/httpd.conf

Since such scripts must be run as root user I wanted to concote a little script to check I had used sudo to run the commands (as I have a habit of forgetting!). Firstly I came up with the following:

#!/bin/sh
# verify-su
umask 222
touch /tmp/user-status
echo `whoami` 2> /dev/null >| /tmp/user-status
if [ $? -ne 0 ] ; then
  if [ $# -eq 0 ] ; then
    "This command must be run with root privileges!"
  else
    "$1 must be run with root privileges!"
  fi
  exit 1
fi

\rm /tmp/user-status

exit 0

A file is created with read only permissions (by temporarily changing umask) and then the script attempts to write to it. The output redirection to file will only succeed if the script is run as root (the superuser).

In running this without the rm command I discovered that a script executed with sudo will return root from the whoami command instead of the user name I am currently logged in with. So this could actually be simplified considerably to:

if [ `whoami` != 'root' ] ; then
  # etc … 
  exit 1
else
  exit 0
fi

There is always a simpler way to do things!

Posted on Monday, Jun 20, 2005 at 19:12:51.