Welcome to Informational Commands. After watching this video, you will be able to: Find user and operating system information. View system disk usage. Monitor running processes
and their resource usage. Print strings, variables, and dates Display manuals for commands You can use informational
commands in your terminal to display user information about your system. ​ User info commands are useful when you need
to verify the identity of the current user or determine which user account is running
a particular command or process. For example, the command “whoami” displays
the current user’s username. The “whoami” command takes no arguments
and has no options. Here you see a usage example for someone logged in
as user “John Doe.” Similarly, the “id” command
returns the user or group ID, which is a number assigned to each
user or group in the Linux system. In this example, using “id” with
the “minus u” option returns the numerical ID of the user. If you would like the name
corresponding to the numerical user ID, add the “minus n” option. The “uname” command, which stands for “Unix name”, returns OS information such as the
kernel name and version number. This can be used to identify the
type of system you are working on or diagnose system-related issues. Entering the uname command returns
the name of the operating system, which in this case is Darwin. Including the “minus s” and
“minus r” options returns both the OS name and its version. You can also view more
detailed version information using the “minus v” option. You can use the “df”, or “disk free” command
to display your system’s disk usage. It can be useful in situations
where you need to monitor disk usage or check the available space
on a particular file system. For example, entering “df minus h
tilde”, displays the following table, which is specific to your home directory,
represented by the tilde symbol. In this table, you can see all the
disks mounted on your home directory. In Linux, you can “mount” a disk onto a directory,
which means that the file system of that disk becomes accessible through that directory. The table also displays the percentage
of storage used on each disk. The “minus h” option makes
the output “human readable, expressing disk space in units like Gigabytes and Terabytes instead of Bytes. To view disk usage on all filesystems, you can simply type “df minus h”
without specifying a directory. The output includes the size, capacity used,
and available space for each filesystem. To see the currently running
processes on your system, you can use the “ps”, or “process status” command. This is helpful when you need
to monitor or manage processes. Using “ps” with the “minus e”
option will list all processes running on the system, regardless
of which user started them. The “ps” command displays information such as
the name of each running process, the process ID, and the time in minutes and seconds
that each process has been running. The “top”, or “table of processes”
command acts as a task manager and will show a table running
processes and their resource usage. This command comes in handy when you
need to monitor system performance or identify resource-heavy processes. Here we show a usage example
with the “minus n” option and the number “3” to display
the top three running tasks: Chrome, top, and Spotify. By default, tasks are sorted by CPU usage. This is a simplified output of
the “top” command for this video, but “top” provides many other details such as memory usage and the executable file location. Although simple, the "echo"
command in Linux is a powerful tool to display text or variables on
the terminal or in a shell script. Entering just “echo” is similar to
telling the terminal to print nothing, and it will return a newline. If you would like to echo a
single word such as “hello”, you can simply type “echo hello”, and
the terminal will return the word. Strictly speaking, you don't need
to add quotes around a string with spaces for echo to work as expected, but it's considered best
practice to include quotes. Using echo with a quoted string returns the
quoted contents, “Learning Linux is fun!" Additionally, you can view
the value of a variable, such as our system’s “PATH” variable, by typing a dollar sign
followed by the variable name. This can be helpful when
troubleshooting or scripting. Here you can see each path of your system’s
PATH variable, delimited by colons. Another helpful command is “date,” which
displays the current system date and time. Entering “date” returns the default date format: the day of the week, the day, month,
year, time, and the time zone. You can also extract certain parts of
the date to print, like in this example. To format the output, encapsulate
within quotes a combination of text and control characters preceded by a “plus” sign. Format controls are indicated with the % symbol. In this case, “percent j” and “percent Y” output the numerical day of the year and
the year itself, respectively. This command prints “97”, for
the 97thth day of the year, the words “day of”, and the year, “2023”. Notice how “percent Y” is
replaced by the year 2023. Finally, here is another example to show how you can further combine format controls
with text to print unique strings. By bringing together controls like “percent
A”, “percent j,” and “percent Y” with text, you can print a line that tells you the
day of the week, the day, and the year. This video has only covered
the basics of these commands. If you want to learn more
about how to use a command, you can use the “man”, or “manual,” command. All default Linux commands come with a
manual that you can display using “man.” For example, entering “man ID” will
display the manual for the “ID” command. The manual will provide a basic summary of what
the command does, such as “return user identity”. Also listed are the options for the
“ID” command, such as “minus a.” Square brackets indicate optional parameters, such
as “user,” which allows you to specify a username. The “man” command also provides a more
detailed description of the command, which explains it in greater detail. The “man” command even has its own “man” page—you can use it to learn more about
the manual command and its uses. In this video, you learned how to: Get user information with the
"whoami" and "id" commands, Get operating system information
using the “uname” command, Check system disk usage using the "df" command, Monitor processes and resource
usage with “ps" and "top", Print string or variable value using "echo", Print and extract information about
the date with the “date" command, And read the manual for any command using “man”.