Unix System Calls

     UNIX system calls are used to manage the file system, control processes,
     and to provide interprocess communication.  The UNIX system interface
     consists of about 80 system calls (as UNIX evolves this number will
     increase).  The following table lists about 40 of the more important
     system call:

 GENERAL CLASS              SPECIFIC CLASS                 SYSTEM CALL
     ---------------------------------------------------------------------
     File Structure             Creating a Channel             creat()
     Related Calls                                             open()
                                                               close()
                                Input/Output                   read()
                                                               write()
                                Random Access                  lseek()
                                Channel Duplication            dup()
                                Aliasing and Removing          link()
                                Files                          unlink()
                                File Status                    stat()
                                                               fstat()
                                Access Control                 access()
                                                               chmod()
                                                               chown()
                                                               umask()
                                Device Control                 ioctl()
     ---------------------------------------------------------------------
     Process Related            Process Creation and           exec()
     Calls                      Termination                    fork()
                                                               wait()
                                                               exit()
                                Process Owner and Group        getuid()
                                                               geteuid()
                                                               getgid()
                                                               getegid()
                                Process Identity               getpid()
                                                               getppid()
                                Process Control                signal()
                                                               kill()
                                                               alarm()
                                Change Working Directory       chdir()
     ----------------------------------------------------------------------
     Interprocess               Pipelines                      pipe()
     Communication              Messages                       msgget()
                                                               msgsnd()
                                                               msgrcv()
                                                               msgctl()
                                Semaphores                     semget()
                                                               semop()
                                Shared Memory                  shmget()
                                                               shmat()
                                                               shmdt()
     ----------------------------------------------------------------------

     [NOTE:  The system call interface is that aspect of UNIX that has
     changed the most since the inception of the UNIX system.  Therefore,
     when you write a software tool, you should protect that tool by putting
     system calls in other subroutines within your program and then calling
     only those subroutines.  Should the next version of the UNIX system
     change the syntax and semantics of the system calls you've used, you
     need only change your interface routines.]

Original Link: http://www.di.uevora.pt/~lmr/syscalls.html