Timing Shell Commands in Bash

When working in a Unix-like environment, timing the execution of shell commands is a useful way to measure the performance of various operations. Bash provides a couple of approaches for timing shell commands: using the /usr/bin/time command or setting the TIMEFORMAT variable.

Using /usr/bin/time Command

The /usr/bin/time command is a versatile utility that can provide information about the resources used by a process, including the execution time. To time a command using /usr/bin/time, you can use the following syntax:

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/usr/bin/time -f '%E' <command>

In this case, <command> should be replaced with the actual command you want to time. For example, to time the execution of the sleep command for 5 seconds, you would run:

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/usr/bin/time -f '%E' sleep 5

The -f '%E' flag specifies the format in which the output should be displayed. %E represents the elapsed time in a human-readable format (hours:minutes:seconds).

Using TIMEFORMAT Variable

Bash also provides the TIMEFORMAT variable, which you can use to customize the output format when timing commands. The syntax is as follows:

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TIMEFORMAT='<format>' time <command>

Here, <format> should be replaced with the desired output format, and <command> should be replaced with the command you want to time. For instance, to time the sleep command for 5 seconds and display a custom message along with the execution time, you could use:

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TIMEFORMAT='It takes %R seconds to complete this task...' time sleep 5

In this example, %R is a placeholder that will be replaced with the actual execution time in seconds.

Conclusion

Both /usr/bin/time and the TIMEFORMAT variable offer convenient ways to measure the execution time of shell commands. Choose the method that best suits your needs and preferences. Keep in mind that these approaches are particularly useful for benchmarking and performance analysis when dealing with various tasks in a Unix-like environment.