- Real time: This is the time as measured either from some standard point (calendar time) or from some fixed point (typically the start) in the life of a process (elapsed or wall clock time). Obtaining the calendar time is useful to programs that, for example, timestamp database records or files. Measuring elapsed time is useful for a program that takes periodic actions or makes regular measurements from some external input device.
- Process time: This is the amount of CPU time used by a process. Measuring process time is useful for checking or optimizing the performance of a program or algorithm.
10 Times and Dates
10.1 Calendar Time
10.2 Time-Conversion Functions
10.2.1 Converting time_t to Printable Form
10.2.2 Converting Between time_t and Broken-down Time
10.2.3 Converting Between Broken-down Time and Printable Form
10.5 Updating the System Clock
10.6 The Software Clock (Jiffies)
10.7 Process Time