Linux Command Line

Task 2: Running Familiar Commands

Step 1: Using Auto-complete and Basic System Information

I started by typing "whoa" and pressing Tab, which activated the auto-complete feature and displayed the full "whoami" command. I pressed Enter and it displayed my current username: ec2-user.

whoami

Next, I entered "hostname -s" and pressed Enter, which displayed a shortened version of my computer's host name, showing something like ip-10.x.x.x.

hostname -s

I then typed "uptime -p" and pressed Enter to see the uptime of my system in an easily readable format. This showed me how long my Linux AMI had been running, which is useful for troubleshooting purposes.

uptime -p

I noticed that these basic commands can be really helpful when I need to find my user, IP address, or how long my system has been running.

Step 2: Viewing User Information

Then I ran "who -H -a" and pressed Enter. This displayed detailed information about the users logged into the system, including Name, Line, Time, Idle, PID, Comment, and Exit. I found this useful for seeing who else might be accessing the system and what they're doing.

who -H -a

Step 3: Working with Dates and Time Zones

I was curious about time zones, so I entered "TZ=America/New_York date" and pressed Enter, followed by "TZ=America/Los_Angeles date". These commands showed me the current date and time in both New York and Los Angeles. The output format included the weekday, month, date, time, timezone, and year - for Los Angeles

TZ=America/New_York date TZ=America/Los_Angeles date

If my system time isn't set properly, these commands would show incorrect times.

I learned that some professions use the Julian date format, which continues consecutively throughout the year instead of restarting at the beginning of each month. To see this in action, I entered "cal -j" in my terminal, which displayed Julian dates for the current month.

cal -j

I also tried the "cal -s" and "cal -m" commands to display alternate views of the calendar. The "cal -s" command showed September from Sunday through Saturday, while "cal -m" displayed it from Monday through Sunday.

cal -s cal -m

I discovered there are many options to display calendars and checked the cal man page for more details.

Step 4: Viewing User ID and Group Information

For my last command in this task, I entered "id ec2-user" and pressed Enter to see my unique ID and group information. This showed my user ID, group ID, and all the groups that I'm a part of as the ec2-user.

id ec2-user

Task 3: Improving Workflow Through History and Search

In this task, I worked on easing my overall workload by reusing commands through search techniques, manual visualization of the bash history log, and reuse of the last command.

Step 1: Viewing Command History

I started by viewing my current bash history. I entered "history" and pressed Enter. In the output, I could see all the commands I had used in Task 2, listed in chronological order.

history

Step 2: Using Reverse History Search

To search my previous command history, I pressed CTRL+R to bring up a reverse history search. In this search feature, I entered "TZ" and pressed Tab. This brought up my previous use of the date command that I could then edit. Using the arrow buttons, I was able to edit the command inline.

CTRL+R

This history searching feature gave me the ability to edit commands that I had previously run. I needed to use Tab autocomplete to edit and run the commands.

Step 3: Rerunning the Last Command

Next, I entered "date" into the terminal and pressed Enter. Then I entered "!!" and pressed Enter. This allowed me to rerun the most recent command (which was "date") without having to retype it.

date !!

This exercise taught me valuable techniques for navigating the Linux command line more efficiently, particularly by leveraging command history and search functionality to avoid repetitive typing.