# This script uses the 'ps' command to view all active processes on the system.
# The 'aux' option is used to display all processes from all users.

# The '$' symbol indicates that the following command should be executed in the terminal.

# The 'ps' command is used to report a snapshot of the current processes.
# The 'aux' option specifies the format of the output to include all processes.

$ ps aux

# This script displays a list of all currently running processes along with their respective PID (process ID), username, and resource usage.

# The output may look something like this:

# USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
# root         1  0.0  0.2 396840 25720 ?        Ss   Mar05   0:00 /sbin/init
# ...

# The following code uses the `ps` command to retrieve information about running processes and pipes it to the `awk` command for formatting.

ps aux | awk '{
    # The `ps` command with the `aux` option displays all processes for all users in a user-oriented format.
    # The output is then piped to the `awk` command for further processing.

    # The `awk` command uses the `print` function to display the desired fields from the `ps` output.
    # The fields are separated by spaces and can be accessed using the `$` symbol followed by the field number.

    # The first line of the `ps` output contains the column headers, so it is skipped using the `NR` variable.
    if (NR > 1) {
        # The `printf` function is used to format the output in a specific way.
        # The `%10s` format specifier ensures that the field is displayed in a 10-character wide column.
        # The `%5.1f` format specifier ensures that the field is displayed as a floating point number with one decimal place.
        # The `%6.1f` format specifier ensures that the field is displayed as a floating point number with one decimal place.
        # The `%8s` format specifier ensures that the field is displayed in a 8-character wide column.
        # The `%s` format specifier ensures that the field is displayed as a string.
        printf("%10s %6s %5s %6s %6s %8s %8s %8s %s\n", $1, $2, $3, $4, $5, $6, $7, $8, $11);
    }
}'

# The output of the `awk` command is then displayed, showing the desired fields in a formatted table.

# This script uses the 'ps' command to view processes owned by a specific user.
# The 'aux' option displays all processes, including those owned by other users.
# The output is then piped to the 'grep' command, which filters the results based on the given username.

# The '$' symbol indicates that this is a command to be executed in the terminal.

# The 'ps' command displays information about active processes on the system.
# The 'aux' option specifies the format of the output to include all processes.

# The '|' symbol is used to pipe the output of one command to another.

# The 'grep' command searches for a specific pattern in the given input.
# In this case, it will filter the output of 'ps aux' to only include processes owned by the user 'jdoe'.

# The 'jdoe' in the command is the username we want to filter by.

# The final result will be a list of processes owned by the user 'jdoe'.

# This script uses the 'pgrep' and 'ps' commands to display all active processes 
# that are currently running under the 'jdoe' account. It also provides additional 
# information about a specific process, such as its command line arguments and 
# environment variables.

# The 'pgrep' command searches for processes based on their name or other attributes.
# In this case, it searches for processes with the name 'firefox' and returns their 
# process IDs (PIDs).

# The '&&' operator allows for the execution of multiple commands in a single line. 
# In this case, the 'ps' command will only be executed if the 'pgrep' command is 
# successful.

# The '-o' flag for the 'ps' command specifies the output format. In this case, 
# 'pid,args' will display the PID and command line arguments for each process.

# The '--no-headers' flag for the 'ps' command removes the header from the output.

# The '$()' syntax allows for the output of one command to be used as an argument 
# for another command. In this case, the output of 'pgrep firefox' will be used as 
# the argument for the 'ps' command.

# Overall, this script will display the PID and command line arguments for all 
# active processes with the name 'firefox' that are running under the 'jdoe' account.

$ pgrep -u jdoe firefox && ps -o pid,args --no-headers $(pgrep -u jdoe firefox)

# This script kills a process by its PID (process ID)
# It takes in the PID as an argument and uses the 'kill' command to terminate the process

# First, we need to get the PID of the process we want to kill
# We can use the 'ps' command to list all currently running processes
# We then use 'grep' to filter the results and only show processes with 'firefox' in their name
# Finally, we use 'awk' to extract the PID from the results and store it in a variable called 'PID'
PID=$(ps aux | grep firefox | awk '{print $2}')

# Now that we have the PID, we can use the 'kill' command to terminate the process
# We use the '-9' flag to force the process to terminate
# We pass in the PID variable as an argument to the 'kill' command
kill -9 $PID

# Note: It is important to use the '-9' flag when killing a process as it ensures the process is terminated immediately
# If we do not use this flag, the process may continue running in the background and cause issues later on
# Also, it is important to note that this script will only work for processes with 'firefox' in their name
# If we want to kill a process with a different name, we would need to modify the 'grep' command accordingly
# Additionally, this script assumes that there is only one instance of Firefox running

# Overall, this script is a simple and quick way to kill a process by its PID without having to manually find and terminate it.