UNIVERSITY OF ATHENS DEPARTMENT OF INFORMATICS & TELECOMMUNICATIONS WWoorrkkiinngg wwiitthh tthhee UUnniixx OOSS Maria Fragouli Dimitris Leventis Argyris Petropoulos Alex Delis AN INTRODUCTION TO UNIX CONTENTS 1. INTRODUCTION TO UNIX .................................................................................... 1 2. UNIX SHELLS.......................................................................................................18 3. C PROGRAMMING ...............................................................................................25 4. UNIX TOOLS ........................................................................................................38 5. DEVELOPMENT TOOLS.......................................................................................51 6. C LIBRARIES........................................................................................................64 7. INTRODUCTION TO KERNEL ..............................................................................80 8. PROCESSES (I) .....................................................................................................93 9. PROCESSES (II) ..................................................................................................122 10. I/O SUBSYSTEM ...............................................................................................143 11. INTERPROCESS COMMUNICATION ................................................................153 12. PROCESS SCHEDULING...................................................................................169 13. BUFFER CACHE ...............................................................................................180 14. UNIX ADMINISTRATION .................................................................................187 15. UNIX SECURITY ..............................................................................................200 TABLE OF FIGURES Figure 1. Data Structures for Processes................................................................................ 85 Figure 2. Process States and Transitions .............................................................................. 85 Figure 3. Sample Code Creating Doubly linked List ............................................................ 85 Figure 4. Incorrect Linked List because of Context Switch .................................................. 86 Figure 5.Multiple Processes Sleeping on a Lock .................................................................. 86 Figure 6. Process State ........................................................................................................ 99 Figure 7. Processes and Regions........................................................................................ 100 Figure 8. Mapping Virtual Addresses ................................................................................ 101 Figure 9. Changing Mode from User ................................................................................. 101 Figure 10. Memory Map of u area in the Kernel ................................................................ 101 Figure 11. Components of Context of a Process................................................................. 102 Figure 12. Sample Interrupt Vector.................................................................................... 102 Figure 13. Handling Interrupts........................................................................................... 102 Figure 14. Example of Interrupts ....................................................................................... 103 Figure 15. Algorithm for System Calls Invocations........................................................... 103 Figure 16. Stack configuration for creat system call........................................................... 103 Figure 17. Steps for a Context Switch................................................................................ 103 Figure 18. Pseudo-Code for Context Switch ...................................................................... 103 Figure 19. Process system calls.......................................................................................... 104 Figure 20. Algorithm for fork ............................................................................................ 104 Figure 21. Fork Creating New Process Context.................................................................. 105 Figure 22. Example of Parent and Child Share File A ........................................................ 105 Figure 23. Use of Pipe, Dup and Fork................................................................................ 106 Figure 24. Checking and Handling Signals ........................................................................ 107 Figure 25. Recognizing Signals ......................................................................................... 107 Figure 26. Algorithm for Handling Signals ........................................................................ 108 Figure 27. Driver Entry Points........................................................................................... 143 Figure 28. Block and Character Device Switch Tables....................................................... 143 Figure 29. Opening a Device ............................................................................................. 144 Figure 30. Closing a Device .............................................................................................. 144 Figure 31. Reading Disk Data - block & raw interface....................................................... 145 Figure 32. Data Sequence and Data Flow through Line Dicsipline..................................... 146 Figure 33. Removing characters from a Clist ..................................................................... 147 Figure 34. Placing characters on a Clist ............................................................................. 147 Figure 35. Writing Data to a Terminal ............................................................................... 148 Figure 36. Flooding Standard Output with Data................................................................. 148 Figure 37. Algorithm for Reading a Terminal ........................................................................1 Figure 38. Contending for Terminal Input Data ................................................................. 149 Figure 39. Raw Mode - Reading 5 character Bursts ........................................................... 150 Figure 40. Polling a Terminal ............................................................................................ 150 Figure 41. Loggin in.......................................................................................................... 151 Figure 42. A Stream after Open......................................................................................... 151 Figure 43. Pushing a Module onto a Stream....................................................................... 152 Figure 44. Windowing VT................................................................................................. 152 Figure 45. Pseudo-code for Multiplexing Windows ........................................................... 152 Figure 46. Process Scheduling........................................................................................... 170 Figure 47. Range of Process Priorities ............................................................................... 171 Figure 48. Process Scheduling Example ............................................................................ 171 Figure 49. Tie breaker rule ................................................................................................ 173 Figure 50. Fair Share Scheduler......................................................................................... 173 Figure 51. Program Using Timer ....................................................................................... 174 Figure 52. Alarm Call........................................................................................................ 174 Figure 53. Clock Handler .................................................................................................. 175 Figure 54. Invoking Profil system call ............................................................................... 175 Figure 55. Output for Profil Program................................................................................. 175 Figure 56. Algorithm for Allocating Space from Maps ...................................................... 176 Figure 57. Mapping Process Space .................................................................................... 177 Figure 58. Swapping a Process into Memory ..................................................................... 177 Figure 59. Adjusting Memory Map for Expansion Swap.................................................... 177 Figure 60. Algorithm for Swapper ..................................................................................... 178 Figure 61. Thrashing due to Swapping............................................................................... 179 Figure 62. Sequence of Swapping Operations.................................................................... 179 Figure 63. Free List of Buffers .......................................................................................... 180 Figure 64. Buffers on the Hash Queues.............................................................................