linux 8 program theory

The pstree Command

pstree is a small, command line (i.e., all-text mode) program that displays the processes (i.e., executing instances of programs) on the system in the form of a tree diagram. It differs from the much more commonly used (and more complex) ps program in a number of respects, including that the latter shows the processes in a list rather than a tree diagram but provides more detailed information about them. Syntax The basic syntax for pstree is: pstree [options] [pid or username] The square brackets indicate that the items in them are optional. If pstree is used without any options or arguments, that is, by typing pstree and then pressing the ENTER key, the result is a tree diagram that shows all of the processes currently on the system. The processes that are directly connected to the main stem  of the tree are listed by default in alphabetic order. This is in contrast to ps, which by default lists the processes in the sequence in which they were created.