Unix provides a means to measure the time it takes for a job to run using the TIME command. The command uses the Unix timer, so it's as accurate as your system clock is. The command is entered followed by the job it will measure (typically a script) at a shell prompt, as the following:
$ time script
For an example, try entering $ time ls. The time command returns the time it took this list command to provide the contents of the current directory. If you change the priority of the job using the nice command, you can see the impact of that change. For example, $ time nice –n 19 ls should slow down the ls command considerably as the priority is lowered.
Your time will vary depending upon your system's current task load and resources. Depending upon the version of Unix you use you may get real clock times, user time, and system time. The real time measures the number of seconds ticked off by the system clock; system and user time tell you the time it took your system to compete the job.
Barrie Sosinsky is president of consulting company Sosinsky and Associates (Medfield MA). He has written extensively on a variety of computer topics. His company specializes in custom software (database and Web related), training and technical documentation.