Display current username (or user when using sudo)
whoami
sudo whoami
Show currently logged in user
who
Permission details for current user
id
List users for system
users
Display information about system user
finger <username>
Show login history for system (or system reboot history)
last
last reboot
Display the Unix system type being used
uname -a
Display the processor architecture (-p) or machine hardware (-m).
(Examples: Processor arm, i386 / Hardware arm64, x86_64)
uname -p
uname -m
Display system OS information (Linux)
cat /etc/os-release
Show distribution specific version information (Linux)
cat /etc/lsb-release
Display basic system OS information or more detailed system config (macOS)
sw_vers
system_profiler SPSoftwareDataType
Search system commands and display short description
whatis <command>
Show location of command for current user path config
which <command>
Show all locations for command
whereis <command>
Display system uptime, memory, who is logged in and what they are doing
w
System uptime statistics
uptime
Display the machine short hostname
hostname
Display the machine fully qualified hostname
hostname -f
Display real time information about process
top
Display detailed real time information about the system
htop
Show list of running processes
ps aux | less
Show memory usage (in megabytes)
free -m
Network settings including computer IP
ifconfig
Local machine IP
ipconfig getifaddr en0
Show smb info for network volumes
smbutil statshares -a
Output key / value pairs of current environment variables
env
Output current terminal settings
stty -a
Log files location
/var/log
System mail messages for users
/var/mail/<username>
Show mail messages
cat /var/mail/<username>
Empty mail messages (via truncate operator >)
> /var/mail/<username>
Empty mail messages (alternative command)
cat /dev/null > /var/mail/<username>