Intro To 'whoami' Command In Linux

2023-05-26 - By Robert Elder

     I use the 'whoami' command to determine who I am.  The 'whoami' command always shows the current user:

whoami

robert

Using 'sudo' With The 'whoami' Command

     If I use the 'sudo' command to become the 'tomcat' user, the 'whoami' command will print 'tomcat':

sudo -u tomcat whoami

tomcat

     The same thing happens if I use 'sudo' to become the 'postgres' user:

sudo -u postgres whoami

postgres

Example Use Of 'whoami' Command

     The 'whoami' command is very useful for writing automated scripts.  For example, in order to run this 'fdisk' command I need to be the root user:

fdisk -l /dev/sda

     I can write a script called 'show-disk.sh' that uses the 'whoami' command to check the current user before trying to run this command:

#!/bin/bash

if [ "$(whoami)" == "root" ]; then
        fdisk -l /dev/sda
else
        echo "Must be root to run this script."
fi

     If the current user is not the root user, then a helpful error message is printed:

./show-disk.sh

Must be root to run this script.

     Otherwise, if the current user is root then the fdisk command is allowed to run:

sudo ./show-disk.sh

Disk /dev/sda: 1.84 TiB, 2000398934016 bytes, 3907029168 sectors
Disk model: Crucial X6 SSD
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 4096 bytes / 33553920 bytes
Disklabel type: gpt
Disk identifier: 098ECDEF-530E-4249-9BCE-3DF21B249458

Device     Start        End    Sectors  Size Type
/dev/sda1   4096 3907029134 3907025039  1.8T Linux filesystem

     And that's why the 'whoami' command is my favourite Linux command.