How To Find When A Command Is Executed In Linux

This tutorial briefly describes how to find the execution time of a command in Linux and understand the benefits of the execution time of a command in Linux.

First, let's understand how to find the execution time of Linux commands.

Table of contents

• Determine the execution time of a specific command
• Understand the benefits of command execution time
• Summarize

Find command execution time in Linux

To find the execution time of a Linux command, you can use the history command, which displays a list of executed commands, as well as their respective dates and times. How to use it is as follows:

 $ HISTTIMEFORMAT="%d/%m/%y %T " history

This formats the historical output to display the date and time of each command. %d/%m/%y format represents day, month and year, while %T represents time in a 24-hour time.

The example output of the above command is as follows:

 <code>[...] 1362 22/03/24 17:17:20 time sleep 2 1363 22/03/24 17:33:35 HISTTIMEFORMAT="%d/%m/%y %T " history</code>

As the output shows, timestamps have been enabled in my bash history command output. Based on the above output, I executed the time command at 5:17:20 pm on March 22, 2024 .

Alternatively, you can use %F instead of %d/%m/%y . Both are correct.

 $ HISTTIMEFORMAT="%F %T " history

If you are using Fish shell , enable timestamps in the historical command output using the following command:

 history --show-time='%F %T '

On the Zsh shell, the command is:

 history -f

For more details on how to enable timestamps in the history command output of Bash, Fish, and Zsh shells, see the following guide:

• How to enable timestamps in Bash history in Linux
• How to enable timestamp for history command in Fish Shell
• How to enable timestamp for Zsh's history command in Linux

Determine the execution time of a specific command

You may have noticed that the above command shows the execution time of all previous commands. What if you want to know when a specific command is executed? This is very simple!

If you want to know the execution time of a command, you can use the time command. For example:

 $ time your_command_here

This will measure the time required for execution and display the execution time after the command is completed.

Example:

 $ time ls

The output will display three times:

• real (total elapsed time),
• user (time spent in user mode),
• sys (time spent in kernel mode).

Sample output:

 <code>[...] real 0m0.001s user 0m0.001s sys 0m0.000s</code>

For more detailed information on the usage of time commands, we recommend that you refer to the following guide:

• Find the execution time of a command or process in Linux

Understand the benefits of command execution time

Whether you are a system administrator or a programmer, understanding the execution time of commands is very useful for optimizing performance.

There are many benefits to understanding the execution time of commands in Linux:

1. Performance Measurement : It can help you measure the performance of a script or command.
2. Optimization : By determining the execution time of a command, you can optimize your scripts to run more efficiently, reducing the total execution time.
3. Resource usage : time command can also display the process's system resource usage, which is very helpful for viewing the efficiency of a specific command.
4. Bottleneck Identification : If a particular task takes more time than expected, it can help identify performance bottlenecks in a system or script.
5. System Monitoring : For system administrators, understanding execution time is critical to system monitoring and can help with capacity planning and troubleshooting.

Summarize

That's it. In this short tutorial, we discuss a useful Linux tip that quickly helps users find the execution time of a command. Hope it helps you.

Related readings:

• How to clear command line history in Linux
• How to display Bash history without line numbers in Linux
• How to avoid duplicate entries in Bash history in Linux

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