What information does the 'time' command show about a program?

The 'time' command in a Linux environment is specifically designed to provide detailed information about the execution duration of a program. When this command is executed, it typically displays three main types of timing metrics: real time, user CPU time, and system CPU time.

• Real time refers to the total elapsed time from start to finish of the program's execution, encompassing all time, even when the program may be waiting for resources or IO operations to complete.
• User CPU time represents the amount of CPU time spent in user mode, that is, while the program was executing its own code.
• System CPU time indicates the amount of CPU time spent in kernel mode, which often includes time spent executing system calls on behalf of the program.

These metrics are crucial for analyzing performance and understanding how efficiently a program runs. They help developers and system administrators optimize applications, identify bottlenecks, and manage resources effectively, which is why this command’s output is focused on elapsed time and CPU time consumed. Other options such as memory usage statistics, file permissions, or network activity logs are not within the scope of what the 'time' command provides.