Linux what is the time command

Команда time в Linux

Команда time используется для определения того, сколько времени требуется для выполнения данной команды. Это полезно для тестирования производительности ваших скриптов и команд.

Например, если у вас есть два разных сценария, выполняющих одну и ту же работу, и вы хотите знать, какой из них работает лучше, вы можете использовать команду Linux time, чтобы определить продолжительность выполнения каждого сценария.

Версии Time Command

Как Bash, так и Zsh, наиболее широко используемые оболочки Linux, имеют свои собственные встроенные версии команды time, которые имеют приоритет над командой времени Gnu.

Вы можете использовать команду type чтобы определить, является ли время двоичным или встроенным ключевым словом.

Чтобы использовать команду Gnu time, вам необходимо указать полный путь к двоичному файлу времени, обычно /usr/bin/time , использовать команду env или использовать начальную обратную косую черту time которая предотвращает использование обоих и встроенных модулей.

Gnu time позволяет форматировать вывод и предоставляет другую полезную информацию, такую как ввод-вывод памяти и вызовы IPC.

Использование команды времени Linux

В следующем примере мы собираемся измерить время, необходимое для загрузки ядра Linux с помощью инструмента wget :

То, что будет напечатано в качестве вывода, зависит от версии используемой вами команды time:

• реальное или общее или прошедшее (время настенных часов) — это время от начала до конца разговора. Это время с момента нажатия клавиши Enter до момента завершения команды wget .
• user — количество процессорного времени, проведенного в пользовательском режиме.
• system или sys — количество процессорного времени, потраченного в режиме ядра.

Выводы

К настоящему времени вы должны хорошо понимать, как использовать команду времени. Если вы хотите узнать больше о команде Gnu time, посетите страницу руководства time .

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How to Time a Command in Linux

If you want to be a good Linux administrator, therefore you should know time command. It is used to determine how long a given command takes to run.

It is useful for testing the performance of your scripts and commands (ie helps to find execution time for shell scripts or time taken for a command to finish).

How to Use Linux time command

To use time command, just execute time with the command/program you want to run as input. Please check below example

The real signifies the wall clock time the ‘ping’ command took from execution till termination, user and sys are the time taken by ping the user space and kernel space.

How to Make time command writes its output to a file

To write the time command output to a file instead of the print out screen, use the -o command line option, which expects a file name/path as input.

Now we will display ping’s output on stdout, while the time command output will be written to the text file.

Note: We used /usr/bin/time instead of time because the shell built-in time command doesn’t offer the -o option.

How to appends its output to an existent file

To append the time command output to an existent file instead of overwrite it, use the -a command line option.

How to get Detailed output of linux time command

We can use the -v command line option to produce detailed output.

How to customizing time command output

There are a large number of formatting options as shown in the following list

C — Name and command line arguments used
D — Average size of the process’s unshared data area in kilobytes
E — Elapsed time in a clock format
F — Number of page faults
I — Number of file system inputs by the process
K — Average total memory use of the process in kilobytes
M — Maximum resident set the size of the process during the lifetime in Kilobytes
O — Number of file system outputs by the process
P — Percentage of CPU that the job received
R — Number of minor or recoverable page faults
S — Total number of CPU seconds used by the system in kernel mode
U — Total number of CPU seconds used by user mode
W — Number of times the process was swapped out of main memory
X — Average amount of shared text in the process
Z — System’s page size in kilobytes
c — Number of times the process was context-switched
e — Elapsed real time used by the process in seconds
k — Number of signals delivered to the process
p — Average unshared stack size of the process in kilobytes
r — Number of socket messages received by the process
s — Number of socket messages sent by the process
t — Average resident set size of the process in kilobytes
w — Number of time the process was context-switched voluntarily
x — Exit status of the command

We can use the formatting switches as follows:

The output for the above command would be something like this:

If we want to add a new line as part of the format string use the newline character as follows:

Linux Time Command Versions

There are three-time command Versions, Bash, Zsh and Gnu time command. We can use the type command to determine whether time is a binary or a built-in keyword.

Please write your suggestions or comments on time command and for more information use time man pages.

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Команда time в Linux

Например, если у вас есть два разных скрипта, выполняющих одну и ту же работу, и вы хотите знать, какой из них работает лучше, вы можете использовать команду time в Linux для определения продолжительности выполнения каждого скрипта.

Версии команды time

И Bash, и Zsh, наиболее широко используемые оболочки Linux, имеют свои собственные встроенные версии команды time, которые имеют приоритет над командой Gnu time.

Вы можете использовать команду type, чтобы определить, является ли время двоичным или встроенным ключевым словом.

Чтобы использовать команду time в Gnu, вам нужно указать полный путь к двоичному файлу time, обычно /usr/bin/time используйте команду env или начальную обратную косую черту \time которая предотвращает использование обеих и встроенных функций.

Время Gnu позволяет вам форматировать выходные данные и предоставляет другую полезную информацию, такую ​​как память ввода-вывода и IPC-вызовов.

Использование команды Time в Linux

В следующем примере мы собираемся измерить время, необходимое для загрузки ядра Linux, с помощью инструмента wget:

То, что будет напечатано как вывод, зависит от версии команды time, которую вы используете:

• реальное или общее или прошедшее (время настенных часов) – это время от начала до конца вызова. Это время от момента нажатия клавиши Enter до момента завершения команды wget.
• user – количество процессорного time, проведенного в пользовательском режиме.
• system или sys – количество процессорного time, проведенного в режиме ядра.

Заключение

К настоящему time вы должны хорошо понимать, как использовать команду time.

Если вы нашли ошибку, пожалуйста, выделите фрагмент текста и нажмите Ctrl+Enter.

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Display Date And Time In Linux

H ow do I display date and time in Linux using the command line and GUI options?

To display date and time under Linux operating system using command prompt use the date command. It can also display the current time / date in the given FORMAT. We can set the system date and time as root user too.

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	Linux with the terminal application
Est. reading time	3 minutes

Syntax

Open a terminal and type the following command:
date

You can format the date as follows in dd-mm-yy format:
date +»%d-%m-%y»

Simply display the current time:
date «+%T»

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To print the date of the day before yesterday, run:
date —date=’2 days ago’
Want to see the day of year of Christmas in the current year? Try:
date —date=’25 Dec’ +%j
Display the current full month name and the day of the month:
date ‘+%B %d’

Display date and time in Linux using the timedatectl

Most modern Linux distro with systemd use the timedatectl command. It is used to query and change the system clock and its settings, and enable or disable time synchronization services. All you have to do is type the following command:
$ timedatectl

TZ environment variable

The TZ environment tells Linux what time zone you are in. Many times when you want to change your time zone temporarily. For example, you might want to print the current date and time in “America/Los_Angeles” timezone even though you are in “Europe/London”. So we can set TZ, give a command like as follows when using TCSH/CSH:
setenv TZ timezone
For BASH/KSH/SH (see export command:
TZ=timezone; export TZ
Another option:
TZ=»America/Los_Angeles» date
TZ=»Asia/Tokyo» date
Use the following command to print a list of all timezones:
timedatectl list-timezones
timedatectl list-timezones | more
## filter out data using the grep command/egrep command ##
timedatectl list-timezones | grep -i Hong_kong
timedatectl list-timezones | grep -i paris
timedatectl list-timezones | grep -E -i ‘paris|london|kolkata’

The TZ Environment Variable on Linux

GUI Tool: Time Administration

The Time Administration Tool allows you to set the time, date and timezone of your system, as well as setting any time server to synchronize your local time server. Type the following command to start time admin tool:
sudo time-admin
## OR ##
time-admin

Fig.01: Linux Date and Time Administration Tool

How to change date and time settings with Gnome based Linux desktop

First, you need to Settings in Activities and then click Details in the sidebar. Make sure you click Date & Time in the sidebar to open the panel:

Conclusion

In this quick tutorial, you learned about the date command that you can use to see or change the date/time under Linux operating systems. We further explained how to use the GUI tools too. The date command has many more options. See man page by typing the following man command:
$ man date

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Find The Execution Time Of A Command Or Process In Linux

You probably know the start time of a command/process and how long a process is running in Linux and Unix systems. But, how do you know when did the command or process end and/or what is the total time taken by the command/process to complete? Well, It’s easy! There is a utility named ‘GNU time’ that is specifically designed to measure the total execution time of a command or program. Using Time utility, we can easily find the execution time of a command or process in Linux and Unix operating systems. Good thing is ‘time’ command comes preinstalled in most Linux distributions, so you don’t have to bother with installation.

Find The Execution Time Of A Command Or Process In Linux

To measure the execution time of a command/program, just run.

The above commands displays the total execution time of ‘ls’ command. Replace «ls» with any command/process of your choice to find the total execution time.

1. real -refers the total time taken by command/program,
2. user — refers the time taken by the program in user mode,
3. sys — refers the time taken by the program in kernel mode.

We can also limit the command to run only for a certain time as well. Refer the following guide for more details.

time vs /usr/bin/time

As you may noticed, we used two commands ‘time’ and ‘/usr/bin/time’ in the above examples. So, you might be wondering what is the difference between them.

First, let us see what actually ‘time’ is using ‘type’ command. For those who don’t know, the Type command is used to find out the information about a Linux command. For more details, refer this guide.

As you see in the above output, time is both,

• A keyword built into the BASH shell
• An executable file i.e /usr/bin/time

Since shell keywords take precedence over executable files, when you just run time command without full path, you run a built-in shell command. But, When you run /usr/bin/time, you run a real GNU time program. So, in order to access the real command, you may need to specify its explicit path. Clear? Good!

The built-in ‘time’ shell keyword is available in most shells like BASH, ZSH, CSH, KSH, TCSH etc. The ‘time’ shell keyword has less options than the executables. The only option you can use in ‘time’ keyword is -p.

You know now how to find the total execution time of a given command/process using ‘time’ command. Want to know little bit more about ‘GNU time’ utility? Read on!

A brief introduction about ‘GNU time’ program

The GNU time program runs a command/program with given arguments and summarizes the system resource usage as standard output after the command is completed. Unlike the ‘time’ keyword, the GNU time program not just displays the time used by the command/process, but also other resources like memory, I/O and IPC calls.

The typical syntax of the Time command is:

The ‘options’ in the above syntax refers a set of flags that can be used with time command to perform a particular functionality. The list of available options are given below.

• -f, —format — Use this option to specify the format of output as you wish.
• -p, —portability — Use the portable output format.
• -o file, —output=FILE — Writes the output to FILE instead of displaying as standard output.
• -a, —append — Append the output to the FILE instead of overwriting it.
• -v, —verbose — This option displays the detailed description of the output of the ‘time’ utility.
• —quiet — This option prevents the time ‘time’ utility to report the status of the program.

When using ‘GNU time’ program without any options, you will see output something like below.

If you run the same command with the shell built-in keyword ‘time’, the output would be bit different:

Some times, you might want to write the system resource usage output to a file rather than displaying in the Terminal. To do so, use -o flag like below.

As you can see in the output, Time utility doesn’t display the output. Because, we write the output to a file named file.txt. Let us have a look at this file:

When you use -o flag, if there is no file named ‘file.txt’, it will create and write the output in it. If the file.txt is already present, it will overwrite its content.

You can also append output to the file instead of overwriting it using -a flag.

The -f flag allows the users to control the format of the output as per his/her liking. Say for example, the following command displays output of ‘ls’ command and shows just the user, system, and total time.

Please be mindful that the built-in shell command ‘time’ doesn’t support all features of GNU time program.

For more details about GNU time utility, refer the man pages.

To know more about Bash built-in ‘Time’ keyword, run:

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