How To Time A Command In Linux

If you have ever wondered how long a specific command in Linux takes to run, you are not alone. Many developers, data analysts, and system administrators find themselves needing to time Linux commands for various reasons such as optimizing scripts or troubleshooting performance issues.

In this blog post, we’re going to delve into how to time a command in Linux and how to format the output. We will be using the time command which is a handy tool that measures the duration of command execution in Linux.

Usage of the time Command

The syntax of the time command is quite simple. You just need to prefix the command you want to time with the word time. For instance:

        time ls

This will run the ls command and then provide a summary of the time taken.

Formatting the Output

By default, the time command outputs three lines showing the elapsed real time, user CPU time and system CPU time. However, you can customize the format of the output using the -f or –format option followed by a format string.

Here is an example:

        time -f "Time elapsed: %e seconds" ls

In this example, %e is a format specifier that stands for the elapsed real time in seconds. The output will look something like this: “Time elapsed: 0.002 seconds”.

You can use several format specifiers to display the information you need. Here are some of the most useful ones:

  • %e: Elapsed real time in seconds
  • %U: User CPU time in seconds
  • %S: System CPU time in seconds


Timing commands in Linux is a powerful feature, especially when optimizing scripts or troubleshooting performance. The time command is a simple and effective way to measure how long your commands are taking to run. And with the flexibility of output formatting, you can get the information you need in a format that suits you best.

Happy Coding!