Warning:This code must corrctly handle lots of picky little details to meetthe Unix98 standard while simultaneously being as compatible aspossible with the original Linux ps. Don't "fix" something withoutconsidering the impact on all the special-case code. For example,the "tty" format _must_ use "TT" as the header, even though the SysVoutput formats _must_ use "TTY".File overview:display.c     main(), debug code, iterates over processesescape.c      Does stuff like \202 and < to command and environment.global.c      Data + code to init it.help.c        Help message.output.c      Giant tables and lots of output functions.parser.c      Initial command parsing.select.c      want_this_proc() checks a process against flags & listssortformat.c  Parses sort & format specifier lists. Picks output format.stacktrace.c  Debug code, not normally used.../proc/*     Library used to gather data.regression    Regression tests that ought to be run.common.h      Lots of interesting stuff.Makefile      Makefilep             Script used to test ps when the library is not installed.utf           Empty file used to test "ps ut?" unmangling behavior.ps.1          Man page.Compiling:Whatever you do, don't trust the Makefiles. They are severely broken.You can touch top.h and top won't be recompiled, or you can changelibrary files and discover that the library and programs won't berecompiled.Operation:Unless the personality forces BSD parsing, parser.c tries to parse thecommand line as a mixed BSD+SysV+Gnu mess. On failure, BSD parsing isattempted. If BSD parsing fails _after_ SysV parsing has been attempted,the error message comes from the original SysV parse.Control goes to sortformat.c, which must pick apart ambiguous optionslike "O". Failure can reset the whole program and set PER_FORCE_BSD,which means a second trip through parser.c and sortformat.c.The choice of output format happens in sortformat.c. There is a switch()with all the valid format_flags combinations. The SysV and defaultoptions are NULL (unless overridden by personality), which causes atrip through SysV output format generation hackery. Note that thedefault format always goes through there, even if it is for BSD.Formats that came from the switch() (generally BSD, plus overrides)get mangled a bit to support various SysV output modifiers.