Linux / Unix: time Command Examples

I am new Linux and Unix systems user. How do I display the time of the execution of a command/script on Linux or Unix-like operating systems using shell prompt?

You need to use the time command to display the elapsed time during the execution of a command or script.[donotprint]

1. real time
2. user time
3. sys time

Purpose

Run command/programs or script and summarize system resource usage

Syntax

The basic syntax is as follows:

time command

OR

time command arg1 arg2 ... argN

OR

time [options] command arg1 arg2 ... argN

Note: The time command is also built into the BASH/KSH/CSH/TCSH with a different syntax. To run the time command while in the shells, type:

/usr/bin/time -p command/usr/bin/time -p command arg1 arg2

time command examples

To measure the time required to run a program called date, enter:
$ time date
OR
$ /usr/bin/time -p date
Sample outputs:

How do I redirect time command output to a file?

The syntax is as follows to save a record of the time command information in a file called output.time.txt, run:

time date 2> output.time.txt
/usr/bin/time -p date 2> output.time.txt

If above command failed, try the following to save a record of the time command information in a file:

( time date ) 2> output.time.txt
## OR ##
{ time date ; } 2> output.time.txt

Use the cat command to display output on screen:
$ cat output.time.txt

A note about GNU/Linux time command

GNU/Linux user can use the following syntax to write the resource use statistics to file instead of to the standard error stream:
$ /usr/bin/time -o output.time.txt -p date
$ cat output.time.txt
Pass the -a option to append the resource use information to the output file instead of overwriting it. This option is only useful with the -o option:
$ /usr/bin/time -a -o output.time.txt -p sleep 2
$ cat output.time.txt
You can control time command output format using -f FORMAT as follows:
$ /usr/bin/time -f 'FORMAT' -p command
Use FORMAT as the format string that controls the output of time as follows:

In this example, show just the user, system, and total time using format option:
$ /usr/bin/time -f "%E real,%U user,%S sys" sleep 2
$ /usr/bin/time -f "%E real,%U user,%S sys" /path/to/script
Sample outputs:

0:02.00 real,0.00 user,0.00 sys

See also

• time(1) Linux/Unix command man page