Linux command line timing

Get program execution time in the shell

I want to execute something in a linux shell under a few different conditions, and be able to output the execution time of each execution. I know I could write a perl or python script that would do this, but is there a way I can do it in the shell? (which happens to be bash)

11 Answers 11

Use the built-in time keyword:

$ help time time: time [-p] PIPELINE Execute PIPELINE and print a summary of the real time, user CPU time, and system CPU time spent executing PIPELINE when it terminates. The return status is the return status of PIPELINE. The `-p' option prints the timing summary in a slightly different format. This uses the value of the TIMEFORMAT variable as the output format.

real 0m2.009s user 0m0.000s sys 0m0.004s

How is this used on a command like time -p i=x; while read line; do x=x; done < /path/to/file.txt ? It immediatly returns 0.00 unless I don't put anything before the while loop.. what gives?

@natli: While time can time an entire pipeline as-is (by virtue of being a Bash keyword), you need to use a group command ( < . ; . ; >) to time multiple commands: time -p < i=x; while read line; do x=x; done < /path/to/file.txt; >

You can get much more detailed information than the bash built-in time (i.e time(1), which Robert Gamble mentions). Normally this is /usr/bin/time .

Editor’s note: To ensure that you’re invoking the external utility time rather than your shell’s time keyword, invoke it as /usr/bin/time . time is a POSIX-mandated utility, but the only option it is required to support is -p . Specific platforms implement specific, nonstandard extensions: -v works with GNU‘s time utility, as demonstrated below (the question is tagged linux); the BSD/macOS implementation uses -l to produce similar output — see man 1 time .

Example of verbose output:

$ /usr/bin/time -v sleep 1 Command being timed: "sleep 1" User time (seconds): 0.00 System time (seconds): 0.00 Percent of CPU this job got: 1% Elapsed (wall clock) time (h:mm:ss or m:ss): 0:01.05 Average shared text size (kbytes): 0 Average unshared data size (kbytes): 0 Average stack size (kbytes): 0 Average total size (kbytes): 0 Maximum resident set size (kbytes): 0 Average resident set size (kbytes): 0 Major (requiring I/O) page faults: 0 Minor (reclaiming a frame) page faults: 210 Voluntary context switches: 2 Involuntary context switches: 1 Swaps: 0 File system inputs: 0 File system outputs: 0 Socket messages sent: 0 Socket messages received: 0 Signals delivered: 0 Page size (bytes): 4096 Exit status: 0 

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Measure Execution Time in Linux Command Line: Tips and Tricks

Learn how to measure execution time in Linux command line using built-in utilities like time command and date utility. Optimize system performance and identify bottlenecks with these tips and tricks.

• The time command
• The date utility
• Calculate the Execution Time of a Command
• Other useful tips
• Advanced usage of the time command
• Additional options for the time command
• Other code samples for measuring execution time in Linux command line
• Conclusion
• How to measure execution time in Linux?
• How to check execution time of shell script?
• How do you calculate execution time of a program?

The Linux command line provides several built-in utilities that can be used to measure the execution time of a command or process. Measuring the execution time of a command or process can help optimize system performance and identify bottlenecks. In this blog post, we will explore some of the key points, important points, and helpful points related to measuring execution time in the Linux command line.

The time command

The time command is a built-in shell keyword that can be used to execute a command and print a summary of the real time, user CPU time, and system CPU time spent by the command. The time command can be used with various options, such as -p to print the time in a portable format and -f to specify a format string. The time command can be used to measure the execution time of a single command or a pipeline of commands.

The syntax for using the time command is:

time [options] command [arguments. ] 

Here, options are the various options that can be used with the time command, command is the command that you want to measure the execution time of, and arguments are any arguments that you want to pass to the command.

To measure the execution time of a command, simply prefix the command with the time command. For example, to measure the execution time of the ls -l command, you would use the following command:

This will output the execution time of the ls -l command in the following format:

real 0m0.005s user 0m0.001s sys 0m0.003s 

Here, real is the real time taken by the command, user is the amount of CPU time spent in user-mode code, and sys is the amount of CPU time spent in kernel-mode code.

Real-life example

Let’s say we want to measure the execution time of the ls -l command. We can simply use the time command as shown below:

This will output the execution time of the ls -l command as shown below:

real 0m0.005s user 0m0.001s sys 0m0.003s 

The date utility

The date utility can also be used to measure the execution time of a command by capturing the start and end time of the command and computing the difference between them. The date utility can be used in combination with other commands, such as echo, to capture the start and end time of a command.

The syntax for using the date utility is:

Here, %s represents the number of seconds since the Unix epoch, and %N represents the number of nanoseconds.

To capture the start and end time of a command, you can use the following syntax:

start=$(date "+%s.%N"); command; end=$(date "+%s.%N"); echo "Execution time: $(echo "$end - $start" | bc) seconds" 

Here, start captures the start time of the command, command is the command that you want to measure the execution time of, end captures the end time of the command, and the echo statement computes the difference between the start and end times and outputs the execution time in seconds.

Real-life example

Let’s say we want to measure the execution time of the sleep 5s command. We can use the date utility as shown below:

start=$(date "+%s.%N"); sleep 5s; end=$(date "+%s.%N"); echo "Execution time: $(echo "$end - $start" | bc) seconds" 

This will output the execution time of the sleep 5s command as shown below:

Execution time: 5.005383294 seconds 

Calculate the Execution Time of a Command

Using time command to track the running execution time of other commands in linuxStore Duration: 10:27

Other useful tips

Using tcsh and setting time to time each command

If you are using the tcsh shell, you can set the time shell variable to time each command. To do this, add the following line to your .tcshrc file:

This will time each command that you execute in the tcsh shell.

/usr/bin/time -v COMMAND or command

You can also use the /usr/bin/time command to measure execution time . This command provides more detailed information about the command’s resource usage, such as memory usage and I/O statistics.

The syntax for using the /usr/bin/time command is:

Here, command is the command that you want to measure the execution time of.

The time() function in shell scripts

In shell scripts, you can use the time() function to echo the time and measure execution time. The syntax for using the time() function is:

Here, command is the command that you want to measure the execution time of.

Advanced usage of the time command

Measuring the wall clock time, user CPU time, and system CPU time of a command

The time command can be used to measure the wall clock time, user CPU time, and system CPU time of a command. The syntax for measuring the wall clock time is:

The syntax for measuring the user CPU time and system CPU time is:

Here, %U represents the user CPU time, %S represents the system CPU time, and %E represents the elapsed time.

Measuring the execution time of a program written in any programming language

The time command can be used to measure the execution time of a program written in any programming language, not just shell scripts. To do this, simply prefix the program with the time command. For example:

This will measure the execution time of the program.py program.

Measuring the execution time of a command and storing the output in a file for later analysis

The time command can be used to measure the execution time of a command and store the output in a file for later analysis. The syntax for doing this is:

/usr/bin/time --format="%E %U %S" -o output.txt command 

Here, —format=»%E %U %S» specifies the format of the output, and -o output.txt specifies the output file.

Real-life example

Let’s say we want to measure the execution time of the a.out program and store the output in a file. We can use the time command as shown below:

/usr/bin/time --format="%E %U %S" -o output.txt ./a.out 

This will measure the execution time of the a.out program and store the output in the output.txt file.

Additional options for the time command

Capturing the output and error output of a command to files

The time command can be used to capture the output and error output of a command to files. The syntax for doing this is:

time command > output.txt 2>&1 

Here, > redirects the output to the output.txt file, and 2>&1 redirects the error output to the same file.

Capturing the input and output of a command to files

The time command can be used to capture the input and output of a command to files. The syntax for doing this is:

Here, < redirects the input from the input.txt file, and >redirects the output to the output.txt file.

Capturing the output of a command in a specific format

The time command can be used to capture the output of a command in a specific format. The syntax for doing this is:

time sh -c 'command | sed "s/^/$(date +%s.%N) /" > output.txt' 

Here, sh -c runs the command in a sub-shell, sed is used to prefix each line of output with the current timestamp, and > redirects the output to the output.txt file.

Setting resource limits for a command

The time command can be used to set resource limits for a command, such as limiting CPU usage or memory usage. The syntax for doing this is:

timeout [options] time command 

Here, timeout sets the resource limits, time measures the execution time, and command is the command that you want to measure the execution time of.

Real-life example

Let’s say we want to measure the execution time of the ls -l command and capture the output and error output in a file. We can use the time command as shown below:

time -o output.txt -a -f "real:%e user:%U sys:%S" ls -l > output.txt 2>&1 

This will measure the execution time of the ls -l command and capture the output and error output in the output.txt file.

Other code samples for measuring execution time in Linux command line

Conclusion

Measuring the execution time of a command or process can be helpful in optimizing system performance and identifying bottlenecks. The Linux command line provides several built-in utilities, such as the time command and the date utility, that can be used to measure execution time. By using advanced options and combining utilities, you can capture detailed information about the execution time of commands and processes in the Linux command line.

Frequently Asked Questions — FAQs

What is the purpose of measuring execution time in Linux command line?

Measuring execution time in Linux command line can help optimize system performance and identify bottlenecks. It can also help in debugging and understanding the behavior of a command or process.

How can I measure the execution time of a single command in Linux command line?

You can use the built-in time command with the command you want to measure the execution time for. For example, «time ls -l» will measure the execution time of the ls -l command.

Can I measure the execution time of a pipeline of commands in Linux command line?

Yes, the time command can be used to measure the execution time of a pipeline of commands by enclosing them in parentheses. For example, «(command1 | command2) | command3» can be measured using «time (command1 | command2) | command3».

Are there any other utilities that can be used to measure execution time in Linux command line?

The date utility can also be used to measure the execution time of a command by capturing the start and end time of the command and computing the difference between them.

Can I measure the execution time of a program written in any programming language using the time command?

Yes, the time command can be used to measure the execution time of a program written in any programming language, not just shell scripts.

How can I capture detailed information about the execution time of a command or process in Linux command line?

You can use advanced options and combine utilities to capture detailed information about the execution time, such as capturing the output and error output to files, setting resource limits, and capturing input and output in a specific format.

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