Linux Time Command

Time command is useful when you want to determine the command execution time. Generally, it’s useful to test the performance of the commands and scripts. In this guide, we will cover how to use the time command in Linux.

When you are writing multiple script which doing same job and want to choose better one by performance, you can use the time command to test the execution time of each script.

Time Command Versions#

The most widely used Linux shells Bash and Zsh have their built-in versions of the time command which is better than the Gnu time command.

Use the type command to determine whether the time is a binary or a built-in keyword.

type time

# Bash
time is a shell keyword

# Zsh
time is a reserved word

# GNU time (sh)
time is /usr/bin/time

In Gnu time command, you need to specify the full path /usr/bin/time to the time binary. Use the env command or use a leading backslash \time which prevents both and built-ins from being used.

You can format the output and show other useful information like memory I/O and IPC calls using the Gnu time.

Using Linux Time Command#

Let’s see an example, to measure the time of download the wordpress using the wget tool:

time wget https://wordpress.org/latest.tar.gz

The output is depends on the version of the time command which your system have:

#Bash
real    0m3.565s
user    0m0.042s
sys     0m0.092s


# Zsh
0.042s user 0.092s system 1% cpu 3.565s total


# GNU time (sh)
0.042user 0.092system 0:03.57elapsed 1%CPU (0avgtext+0avgdata 6060maxresident)k
0inputs+201456outputs (0major+315minor)pagefaults 0swaps

Here,

• The real or total or elapsed is showing the time which taken from start to wget command completed.
• user – amount of CPU time spent in user mode.
• system or sys – It shows the amount of CPU time spent in kernel mode.

Conclusion#

You successfully learned how to use the time command. You can learn more about the Gnu time command by visiting the time man page.

If you have any question or feedback, please leave a comment below.