Description
-- | --
whoami | Print effective userid
id | Print real and effective user and group IDs
awk -F ':' '{print $1}' /etc/passwd | List all users on the system
awk -F ':' '{print $1}' /etc/group | List all groups on the system
last | Show listing of last logged in users
lastlog | Foreach users get the last logged in
for i in $(cat /etc/passwd 2>/dev/null| cut -d":" -f1 2>/dev/null);do id $i;done 2>/dev/null | List uid and groups for each users
grep -v -E "^#" /etc/passwd | awk -F: '$3 == 0 { print $1}' | List all super users accounts
w | Show who is logged on and what they are doing
users or who -a | Print the user names of users currently logged in to the current host
cat /etc/shells | Pathnames of valid login shells
cat /etc/profile | Display default system variables
cat ~/.profile | Display user variables and functions
env | Display environmental variables
route | Display route information
arp -a | Display arp table
cat /etc/resolv.conf | Show configured DNS sever addresses
head /var/mail/root | Try to read root mail
perl -v | Perl version
java -version | Java version
python --version | Python version
ruby -v | Ruby version