time command is a very simple, but useful command line utility in Linux. Essentially, you can think of it as a stopwatch built into the terminal, as it measures the amount of time it takes to execute a specified Linux command.
In this guide, we’ll show you how to use the
time command through various examples, and teach you how to interpret its output. We’ll also show how to use GNU time, which is different than the time utility built into the Bash and zsh shells.
In this tutorial you will learn:
- How to use time command
- How to use GNU time
- How to interpret the output of the time and GNU time commands
|Category||Requirements, Conventions or Software Version Used|
|System||Any Linux distro|
|Other||Privileged access to your Linux system as root or via the
# – requires given linux commands to be executed with root privileges either directly as a root user or by use of
$ – requires given linux commands to be executed as a regular non-privileged user
time vs GNU time
We’ll be discussing two different versions of time in this article, the default time for the Bash shell, and GNU time. Note that there are also other versions of time used on other shells, such as zsh. For the purposes of this guide, we’ll assume you’re using the Bash shell.
To call the Bash time utility, you can simply type the
time command. To use GNU time, specify the full path which should be
$ time (command here) OR $ /usr/bin/time (command here)
time and GNU time examples
In the following example, we’ll use both utilities to measure the time it takes to download a file with wget.
First, with Bash time:
The part we want to pay attention to is the last three lines, which were output by
real 4m12.067s user 0m0.086s sys 0m1.030s
Here’s what this information means:
- real – the actual amount of time it took to run the command
- user – the amount of time the CPU spent in user mode
- sys – the amount of time the CPU spent in kernel mode
And now let’s try the same download, while measuring with GNU time:
We’ll only concern ourselves with the last two lines – the ones from GNU time.
0.05user 0.95system 0:08.64elapsed 11%CPU (0avgtext+0avgdata 7220maxresident)k 0inputs+30488outputs (0major+428minor)pagefaults 0swaps
This outputs the same information as
time, along with some more detailed statistics, and a very human-readable measurement of the CPU usage.
In this guide, we saw how to use the
time and GNU time command line utilities on Linux to measure the amount of time and CPU usage it takes to execute any command we want. These commands are very simple to master, but can come in handy quite often.