With rusage you can get information about the resource usage for a command, e.g. rusage a.out. The resident set size is the size of physical memory used by the process at a certain time. mx is the maximum resident set size. Size is given in pages (4096 Bytes in this case) id is an "integral" value indicating the amount of memory in use by a process while the process is running. This value is the sum of the resident set sizes of the process running when a clock tick occurs. The value is given in pages times clock ticks. Note: it does not take sharing into account. WARNING: The way resident set size is calculated is an approximation and could misrepresent the true resident set size.
