12 UNIX / Linux Time Command Output Format Option Examples

by Himanshu Arora on October 7, 2013

Linux time command is helpful to identify the time taken by a command.

Using Linux time command, you can figure out how much time was taken to execute a command, or shell script, or any other program.

By default, time command executes the given command or program. After execution, it displays the statistics and resources usage on the standard error.

Time command provides several command line options and various format options as explained in this tutorial

1. Basic Time Command Usage Example

Time command syntax:

$ time [-options] <command arg1 arg2 ..>

For example, time command is run on sleep command without any option.

$ /usr/bin/time sleep 2
0.00user 0.00system 0:02.00elapsed 0%CPU (0avgtext+0avgdata 2288maxresident)k
0inputs+0outputs (0major+172minor)pagefaults 0swaps

Let’s now understand some important command line options of this command.

2. Write Time Statistics Output to a File using -o option

This option is to restrict sending the command results to standard error, but writes results into output file. This option overwrites the specified file.

Here is an example :

$ /usr/bin/time -o time.txt sleep 2

$ cat time.txt
0.00user 0.00system 0:02.00elapsed 0%CPU (0avgtext+0avgdata 2288maxresident)k
0inputs+0outputs (0major+175minor)pagefaults 0swaps

3. Append Time Statistics Output to an Existing File using -a option

This option allows appending time command output into file. It is used along with -o option. This option avoids overwriting of content of output file by appending time command output into specified output file.

Here is an example :

$ /usr/bin/time -a -o time.txt sleep 4

$ cat time.txt
0.00user 0.00system 0:02.00elapsed 0%CPU (0avgtext+0avgdata 2288maxresident)k
0inputs+0outputs (0major+175minor)pagefaults 0swaps
0.00user 0.00system 0:04.00elapsed 0%CPU (0avgtext+0avgdata 2288maxresident)k
0inputs+0outputs (0major+176minor)pagefaults 0swaps

4. Display Percentage of CPU used – %P

You can provide output formatting choices using -f option. This option allows user to provide output formatting options. It possibly does overriding the format specified in the environment variable TIME. Following formatting options are described below – %P, %M, %S, %e, %E, %C, %Z, %c, %x.

This option gives percentage of the CPU that the process of command (i.e. run under time command) has got for its execution. This is just user + system times divided by the total running time. It also prints a percentage sign.

$ /usr/bin/time -f "\t%P CPU Percentage" find / -name my-program.sh
/root/my-program.sh
        82% CPU Percentage

Here, command output shows that find command took 82% of CPU.

5. Display Maximum Resident Set Size – %M

This option gives maximum resident set size of the process of command (i.e. run under time command) during its lifetime, in Kilobytes.

$ /usr/bin/time -f "\t%M Max Resident Set Size (Kb)" find / -name my-program.sh
/root/my-program.sh
        8688 Max Resident Set Size (Kb)

Here, command output shows that find command took 8688 KB as maximum resident size of process.

6. Display Total Number of CPU-seconds – %S

This option gives total number of CPU-seconds used by the system on behalf of the process (in kernel mode), in seconds.

$ /usr/bin/time -f "\t%S CPU-seconds" find / -name my-program.sh
/root/my-program.sh
        0.35 CPU-seconds

Here, command output shows that find command took 0.35 CPU-seconds in kernel mode.

7. Display Elapsed Real Time in Seconds – %e

This option gives elapsed real time (i.e. wall clock) used by the process, in seconds.

$ /usr/bin/time -f "\t%e Elapsed Real Time (secs)" sleep 2
        2.00 Elapsed Real Time (secs)

Here, command output shows that sleep command execution elapsed till 2 seconds.

8. Display Elapsed Real Time in Different Format – %E

This option gives elapsed real time (i.e. wall clock) used by the process, in this format – [hours:]minutes:seconds.

$ /usr/bin/time -f "\t%E Elapsed Real Time (format)" sleep 2
        0:02.00 Elapsed Real Time (format)

Here, command output shows that sleep command execution took 0 hour, 0 minute and 2 seconds.

9. Display Program Name and Command Line Arguments – %C

This option gives name and command line arguments of the command (i.e. run under time command).

$ /usr/bin/time -f "\t%C (Program Name and Command Line)" find / -name my-program.sh
/root/my-program.sh
        find / -name my-program.sh test_time (Program Name and Command Line)

Here, time command output shows name of command being run and its command line arguments.

10. Display System Page Size in Bytes – %Z

This option gives system’s page size, in bytes. This is a per-system constant, but it may vary one system to another system.

$ /usr/bin/time -f "\t%Z System Page Size (bytes)" sleep 2
        4096 System Page Size (bytes)

Here, command output shows that sleep command used 4096 bytes as system page size.

11. Display Number of Context Switches – %c

This option gives number of times the process was context-switched involuntarily (because the time slice expired).

$ /usr/bin/time -f "\t%c Context Switches" find / -name my-program.sh
/root/my-program.sh
        254 Context Switches

Here, command output shows that 254 times context switching of process took place during execution of find command under time command.

12. Display Exit Status of a Command – %x

This option gives exit status of the command (i.e. run under time command).

$ /usr/bin/time -f "\t%x Exit Status" top1
/usr/bin/time: cannot run top1: No such file or directory
        127 Exit Status

Here, command output shows that top1 command is failed because this tope1 as a file does not exist.

As per man page of time command, exit status of time command can be following:

  • If command specified to time command was invoked, the exit status is the exit status of command which is run with time command.
  • It is 127 if command specified to time command could not be found.
  • 126 if command specified to time command could be found but could not be invoked.
  • Some other non-zero value (1-125) if something else went wrong.

Finally, there is a difference between executing just “time” and “/usr/bin/time”. We explained this in our earlier introduction to time command article.


Linux Sysadmin Course Linux provides several powerful administrative tools and utilities which will help you to manage your systems effectively. If you don’t know what these tools are and how to use them, you could be spending lot of time trying to perform even the basic administrative tasks. The focus of this course is to help you understand system administration tools, which will help you to become an effective Linux system administrator.
Get the Linux Sysadmin Course Now!

If you enjoyed this article, you might also like..

  1. 50 Linux Sysadmin Tutorials
  2. 50 Most Frequently Used Linux Commands (With Examples)
  3. Top 25 Best Linux Performance Monitoring and Debugging Tools
  4. Mommy, I found it! – 15 Practical Linux Find Command Examples
  5. Linux 101 Hacks 2nd Edition eBook Linux 101 Hacks Book

Bash 101 Hacks Book Sed and Awk 101 Hacks Book Nagios Core 3 Book Vim 101 Hacks Book

{ 6 comments… read them below or add one }

1 Bob October 8, 2013 at 8:03 am

Really useful post. I used it today and helped a lot. Thanks!!!

2 dpminusa October 8, 2013 at 1:33 pm

In example 8, I think the format is differrent in any Linux Distro I use. It shows hundreds of a second as well. Maybe your distro is diferent?

i.e. hh:mm:ss.ss.

Very helpful article. I use the %E with my rsync scripts regularly to monitor for problems and needs for tuning.

3 Jacek October 8, 2013 at 2:03 pm

I am getting an error when I run this command:
$time -o time.txt sleep 2
-o: command not found

real 0m0.069s
user 0m0.056s
sys 0m0.008s

This however works fine:
$ /usr/bin/time -o time.txt sleep 2

$ which time
/usr/bin/time

Why do I have use full path when referencing the command? Bug?

4 devi killada October 8, 2013 at 8:30 pm

These commands are very useful.

5 Jalal Hajigholamali October 9, 2013 at 3:48 am

Hi,

Thanks a lot…

Simple and useful article….

6 dpminusa October 9, 2013 at 4:58 am

@Jacek

Bash has a built-in time command that does NOT support formatting options. If you do not provide the full path name it will be used rather than the advanced time command in the examples.

This implies you need to make sure you have the external time command installed as well. Some distros do not do that by default.

Dan.

Leave a Comment

Previous post:

Next post: