

                   UNIX Bourne Shell Programming


                    Developed by:

                         User Liaison Section, D-7131
                         Denver Office
   
                    [Name and number removed at author's
                     request]

                    Revision Date:  February 7, 1991


I.  INTRODUCTION..............................................  v
     A.  Audience.............................................  v
     B.  Course Objectives....................................  v
     C.  Course Handout Conventions........................... vi

1.  BOURNESHELL OVERVIEW......................................  1
     1.1  What is the BourneShell?............................  2
     1.2  Making a Bourne Shell Script Executable.............  3
     1.3  Tracing Mechanisms..................................  6
     Workshop 1...............................................  9

2.  USER, SHELL, AND READ-ONLY SHELL VARIABLES................ 11
     2.1  User Variables...................................... 11
     2.2  Shell Variables..................................... 14
          2.2.1  HOME......................................... 14
          2.2.2  IFS.......................................... 15
          2.2.3  MAIL......................................... 15
          2.2.4  MAILPATH..................................... 15
          2.2.5  MAILCHECK.................................... 16
          2.2.6  PATH......................................... 16
          2.2.7  PS1.......................................... 17
          2.2.8  PS2.......................................... 17
     2.3  Read-Only User Variables............................ 18
     2.4  Read-Only Shell Variables........................... 19
          2.4.1  Name of the Calling Program.................. 19
          2.4.2  Arguments.................................... 19
          2.4.3  Shift........................................ 21
          2.4.4  Set.......................................... 22
          2.4.5  expr......................................... 23
     Workshop 2............................................... 27

3.  POSITIONAL PARAMETERS..................................... 33
     3.1  Reading Input Into a Shell Variable................. 34
     3.2  Command Substitution................................ 36
     3.3  Comments in BourneShell Scripts..................... 38
     3.4  BourneShell Environment - Exporting Variables....... 39
     Workshop 3............................................... 41

4.  CONTROL CONSTRUCTS:....................................... 45
     4.1  Types of Tests Used with Control Constructs:........ 46
     4.2  Test on Numeric Values.............................. 47
     4.3  Test on Character Strings........................... 47
     4.4  Test on File Types.................................. 49
     4.5  if then............................................. 50
     4.6  if then else........................................ 52
     4.7  if then elif........................................ 54
     4.8  for................................................. 55
     4.9  while............................................... 57
     4.10  until.............................................. 58
     4.11  case............................................... 60
     Workshop 4............................................... 63

5. COMPILING PROGRAMS IN UNIX................................. 67
     5.1  "C": Sample Program with a Main and Two Functions
               in One        ................................. 67
     5.2  "C": Compiling a Program............................ 69
     5.3  "C": Renaming the Executable Module................. 71
     5.4  "C": Giving a Name to the Output File............... 72
     5.5  "C": Producing an Assembly Listing.................. 73
     5.6  "C": Main and Two Functions in Three Separate Source
               Files.......................................... 74
     5.7  "C": Compiling but Not Producing an Executable    
           Module............................................. 75
     5.8  FORTRAN: Sample Program a Main and Two Subroutine... 76
     5.9  FORTRAN: Compiling a Program........................ 77
     5.10  FORTRAN: Renaming the Executable Module............ 79
     5.11  FORTRAN: Giving a Name to the Output File.......... 80
     5.12  FORTRAN: Producing an Assembly Listing............. 81
     5.13  FORTRAN: Main and Two Subroutines in Three Separate
                    Source Files.............................. 82
     5.14  FORTRAN: Compiling But Not Producing an Executable
                    Module.................................... 83
     5.15  FORTRAN: Compiling Object Files to Produce an    
                Executable Module............................. 84
     5.16  COBOL: Sample Program with a Main and Two        
                  Subroutines................................. 85
     5.17  COBOL: Compiling a Program......................... 86
     5.18  COBOL: Running a Program........................... 87
     Workshop 5............................................... 89

6.  UNIX TOOLS................................................ 95
     6.1  Processes........................................... 95
     6.2  Executing a Command................................. 95
     6.3  Process Identification.............................. 95
     6.4  grep: A Pattern Matching Filter..................... 98
          6.4.1  More on Regular Expressions.................. 99
          6.4.2  Closure......................................103
          6.4.3  Some Nice grep Options ......................104
          6.4.4  Summary of Regular Expression Characters.....105
     6.5  sed: Edit a File to Standard Output.................106
     6.6  awk: A Pattern Matching Programming Language........110
     6.7  sort: Sort a File...................................114
     6.8  What Other Useful UNIX Tools are Available..........117
     6.9  Archiver and Library Maintainer.....................118
          6.9.1  ar: Creating an Archive File with Object   
                  Modules.....................................119
          6.9.2  ar: Verifying the Contents of the Archive  
                   File.......................................119
          6.9.3  ar: Removing Duplicate Object Files..........120
          6.9.4  ar: Compiling Main and Archive Files.........120
     Workshop 6...............................................121


7.  VAX DCL TO UNIX SHELL SCRIPT CONVERSION...................125
     7.1  Processes...........................................127
     7.2  Pipes...............................................128
     7.3  Input, Output, and Error Redirection................129
     7.4  Command Structure and File Naming Conventions.......131
     7.5  File Management Commands............................133
     7.6  Metacharacters......................................135
     7.7  Wildcards: Are They Really Wild?....................136
     7.8  Summary.............................................137
     Workshop 7...............................................139

8.  ADVANCED FEATURES OF FTP..................................143
     8.1  Initializing FTP on UMAX............................144
     8.2  Multiple File Transfers.............................145
     8.3  Auto Login Feature..................................146
     8.4  Macros..............................................148
     8.5  Filename Translation................................149
     8.6  Aborting Transfers..................................150
     8.7  More Remote Computer Commands.......................151
     Workshop 8...............................................153

9.  OPTIONAL CHAPTER - KORNSHELL PROGRAMMING..................155
     9.1  KornShell Variables.................................155
     9.2  User Defined Variables..............................157
     9.3  Values of Variables Between Child and Parent
          Processes...........................................158
     9.4  ksh: Aliases........................................159
     9.5  ksh: Command Line Editing...........................161
     9.6  ksh: Interactive Command Line Editing...............162
     9.7  ksh: Functions......................................164
     9.8  ksh: The Select Construct...........................166
     9.9  ksh: Tracing and Conditional Execution..............168
     Workshop 9...............................................169

APPENDIX A - sh...............................................173

APPENDIX B - test.............................................189

APPENDIX C - expr.............................................193

APPENDIX D - ftp..............................................195

APPENDIX E - cc...............................................209

APPENDIX F - f77..............................................219

APPENDIX G - lint.............................................231

APPENDIX H - cb...............................................235

APPENDIX I - ar...............................................237

APPENDIX J - time.............................................243

APPENDIX K - ksh..............................................245

INDEX.........................................................279

I.  INTRODUCTION


A.  Audience


This course is for individuals who have completed "UNIX for
Beginning Users" (or equivalent experience) and want to write UNIX
BourneShell script files.  A script file contains a sequence of
UNIX commands which can be executed by entering one command.  It
is assumed that the student already has a good understanding of the
UNIX operating system, be able to use a UNIX editor, and be
familiar with a computer terminal or typewriter keyboard.


B.  Course Objectives


Upon successful completion of this course the student will be able
to:

     1.   Write moderately complex BourneShell scripts.

     2.   Make a BourneShell script executable.

     3.   Demonstrate how to use the following BourneShell
          commands: shift, exit, expr, test, if then, if then else,
          if then elif, for, while, until, and case.

     4.   Use the following BourneShell constructs: tracing
          mechanisms (for debugging), user variables, BourneShell
          variables, read-only variables, positional parameters,
          reading input to a BourneShell script, command
          substitution, comments, and exporting variables.  In
          addition, test on numeric values, test on file type, and
          test on character strings are covered.

     6.   Create a ".profile" script to customize the user
          environment.

     7.   Use advanced features of File Transfer Protocol (FTP)

     8.   Compile source code into object and executable modules.

     9.   Optional: KornShell programming.  This is of primary
          interest to programmers.

     10.  Convert VMS DCL command files to UNIX Shell.
C.  Course Handout Conventions


There are several conventions used in this handout for consistency
and easier interpretation:


     1.   Samples of actual terminal sessions are single-lined
          boxed.


     2.   User entries are shown in bold print and are underlined.

          exit


     3.   All keyboard functions in the text will be bold.  

          (Ret)               Backspace
          Tab                 Ctrl-F6
          Print (Shift-F7)    Go to DOS (1)

          NOTE:     (Ret) indicates the Return or Enter key located
                    above the right Shift key.


     4.   Examples of user entries not showing the computer's
          response are in dotted-lined boxes.                   
           

     5.   Command formats are double-lined boxed.


     6.   Three dots either in vertical or horizontal alignment
          mean continuation or that data is missing from diagram.

                                                                 
кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г                                                               Г
Г        Multimax, Nanobus, and UMAX are trademarks of          Г
Г        Encore Computer Corporation.                           Г
Г                                                               Г
Г                                                               Г
Г        Annex is a trademark of XYLOGICS, Inc.                 Г
Г                                                               Г
Г                                                               Г
Г        UNIX and Teletype are registered trademarks of         Г
Г        AT&T Bell Laboratories                                 Г
Г                                                               Г
Г                                                               Г
Г        Ethernet is a trademark of Xerox Corporation           Г
Г                                                               Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй
                               NOTES
ммммммммммммммммммммммммммммммммммммммммммммммммммммммммммммммммм
1.  BOURNESHELL OVERVIEW


The BourneShell is both a command-line interpreter and a high-
level programming language.  When it is acting as a command-line
interpreter, it processes commands as you enter them at the command
prompt.  When you use it as a programming language, it processes
commands that are stored in files known as BourneShell scripts. 
This course will show you how to create and execute BourneShell
scripts.  We will explore BourneShell programming including such
features as variables, control structures, processes, and
executable files.


The BourneShell is one of three shells available on most UNIX
systems.  Bourne is the accepted standard for System V UNIX.  The
other shells are being used more and more.  The other shells are
the CShell and the KornShell.  The CShell is BSD (Berkeley Software
Distribution) UNIX. BSD was developed at the University of
California at Berkeley, California. Most of the features found in
the BourneShell are also found in the other shells; there are
differences, however.  The CShell and KornShell are not standard
on UNIX System V but are generally available.


BourneShell scripts allow you to group command lines together and
execute them by entering a single command at the command line. This
allows complex functions to be completed by any user, and
repetitive functions can be completed easily.  Input and output
can also be redirected from a BourneShell script.
1.1  What is the BourneShell?

BourneShell is a high level programming language and a command line
interpreter. 

The command to invoke the BourneShell is:

ЩЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЛ
К  Command Format:  sh [-acefhiknrstuvx] [args]                 К
К                                                               К
К  (See Appendix A for a complete list of options etc)          К
ШЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭМ

A Shell script is an executable plain file that contains UNIX and
shell commands. To execute the shell script type the name of the
script at the prompt. A simple shell script called shell_ex is
shown in the following example. The output from the execution of
the shell is also shown.

Sample Session:

кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г $cat shell_ex                                                 Г
Г echo "This is a very simple shell procedure "                 Г
Г echo "created with the basic echo command "                   Г
Г echo "and three other very basic commands "                   Г
Г echo                                                          Г
Г ps                                                            Г
Г echo                                                          Г 
Г who                                                           Г
Г echo                                                          Г
Г ls                                                            Г
Г $sh shell_ex                                                  Г
Г This is a very simple shell procedure                         Г
Г created with the very basic echo command                      Г
Г and three other very basic commands                           Г
Г                                                               Г
Г PID    TTY     TIME    COMMAND                                Г
Г 10443 rt02120  0:01    sh                                     Г
Г 10427 rt02120  0:04    ksh                                    Г
Г                                                               Г
Г sgavlick  rt021e0   Sep 7   13:26                             Г
Г teacher   rt021b0   Sep 7   14:39                             Г
Г                                                               Г
Г memo                                                          Г
Г class_notes                                                   Г
Г $                                                             Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй
1.2  Making a Bourne Shell Script Executable

A BourneShell script is an ordinary file that contains commands
which can be executed in sequence by entering one command at the
BourneShell prompt.  In order for a script to be executed, it must
first be executable.  This is done with the chmod command.

Sample Session:

кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г $cat shell_ex                                                 Г
Г echo "This is a very simple shell procedure "                 Г
Г echo "created with the basic echo command "                   Г
Г echo "and three other very basic commands "                   Г
Г echo                                                          Г
Г ps                                                            Г
Г echo                                                          Г
Г who                                                           Г
Г echo                                                          Г
Г ls                                                            Г
Г $                                                             Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй

If the ls -l shell_ex command were entered, we would see the
protections assigned to this file.

Sample Session:

кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г $ls -l shell_ex                                               Г
Г -rw-r--r-- 1 teacher class  66 Sep 7 10:24 shell_ex           Г
Г $                                                             Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй

The character in column one is the type of file. 

      -  =  ordinary (plain) disk file

      d  =  directory

      b  =  block special file

      c  =  character special file

      p  =  fifo file ("named pipe") special file

      l  =  symbolic link

          
Notice that the script file in the previous sample session has the
following file protections:

     User   - Read and Write
     Group  - Read
     Other  - Read

No execute permissions have been granted for user, group, or other. 
If we try to execute this script by typing its name, the following
would result.

Sample Session:

кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г $shell_ex                                                     Г
Г shell_ex: execute permission denied                           Г
Г $                                                             Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй

This error message would indicate that execute permission was
denied.  The BourneShell script could not be executed.  To change
the permissions for the BourneShell script, use the chmod command.

Sample Session:

кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г $chmod 755 shell_ex                                           Г
Г $ls -l shell_ex                                               Г
Г -rwxr-xr-x 1 teacher class  66 Sep 7  10:26 shell_ex          Г
Г $                                                             Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй


Now that the permissions have been changed to allow user, group,
and others to execute the file, it will execute properly.
Sample Session:

кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г $shell_ex                                                     Г
Г This is a very simple shell procedure                         Г
Г created with the basic echo command                           Г
Г and three other very basic commands                           Г
Г                                                               Г
Г PID    TTY     TIME    COMMAND                                Г
Г 10443 rt02120  0:01    sh                                     Г
Г 10427 rt02120  0:04    ksh                                    Г
Г                                                               Г
Г sgavlick  rt021e0   Sep 7   13:26                             Г
. teacher   rt021b0   Sep 7   14:39                             .
.                                                               .
.                                                               .


The protections will work as you expect.  Execute permission for
the user will allow you (the owner) to run the BourneShell script.
Group permissions allow anyone in your group to execute the script,
and other permission allows anyone on the system to execute the
script.
1.3  Tracing Mechanisms

It is possible to have a trace made of the BourneShell script as
it executes. This is invaluable for debugging purposes. All that
is required is to give an option to the BourneShell.   This is done
by including an option on the call to "sh". The command to do this
is:

ЩЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЛ
К     Command Format: sh [-acefhiknrstuvx] [args]               К
К                                                               К
К     See Appendix A for a complete list of options etc         К
К                                                               К
ШЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭЭМ

The option to turn on tracing is -x. For an example, let's trace
the execution of the simple script shell_ex.

Sample session:

кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г     $cat shell_ex                                             Г
Г     echo "This is a very simple shell procedure "             Г
Г     echo "created with the basic echo command "               Г
Г     echo "and three other very basic commands "               Г
Г     echo                                                      Г
Г     ps                                                        Г
Г     echo                                                      Г
Г     who                                                       Г
Г     echo                                                      Г
Г     ls                                                        Г
Г     $                                                         Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй

Execute the BourneShell script using the -x option on the call to
the shell. The following sample session shows how to do this and
it shows the results of the trace.
Sample session:

кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г     $sh -x shell_ex                                           Г
Г     + echo This is a very simple shell procedure              Г
Г     This is a very simple shell procedure                     Г
Г     + echo created with the basic echo command                Г
Г     created with the basic echo command                       Г
Г     + echo and three other very basic commands                Г
Г     and three other very basic commands                       Г
Г     + echo                                                    Г
Г                                                               Г
Г     + ps                                                      Г
Г     PID    TTY      TIME       COMMAND                        Г
Г     10443 rt01120   0:01       sh                             Г
Г     10427 rt02120   0:04       ksh                            Г
Г     + echo                                                    Г
Г                                                               Г
Г     + who                                                     Г
Г     sgavlick  rt021e0   Sep 7  13:26                          Г
Г     teacher   rt02120   Sep 7  14:39                          Г
Г     + echo                                                    Г
Г                                                               Г
Г     + ls                                                      Г
Г     memo                                                      Г
Г     class_notes                                               Г
Г     $                                                         Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй

The commands as read from the BourneShell script are indicated by
the plus sign (+). The next line or lines are the results of the
execution of the command. Using this tracing option allows you to
se the execution of each command in the script and see the results
of that execution.
                               NOTES
мммммммммммммммммммммммммммммммммммммммммммммммммммммммммммммммм
Workshop 1

This workshop will reinforce your understanding of the ideas
presented in Chapter 1. Each student is to complete the entire
workshop.

DESK EXERCISES 


     1.   The BourneShell can act as a command line

                                                   
          or a high level                          .  


     2.   The BourneShell is one of three shells generally
          available. What are the other two?


     3.   One advantage of using a shell script is

                                                  .


     4.   The command to call the BourneShell is:

          a.   bourne
          b.   ksh
          c.    b
          d.   sh


     5.   Why would you use tracing?


     6.   What UNIX command do you enter to make a BourneShell
          script executable? 


     That's all
                               NOTES
ммммммммммммммммммммммммммммммммммммммммммммммммммммммммммммммммм
2.  USER, SHELL, AND READ-ONLY SHELL VARIABLES


The BourneShell has no true numeric variables.  It uses string
variables to represent numbers, as well as text.  String variables
are able to take on the value of a string of characters.  There are
three types of variables in the BourneShell.  They are user
variables, BourneShell variables, and Read-only BourneShell
variables.

You can declare, initialize, read, and modify user variables from
a BourneShell script or from the command line.  The BourneShell
itself declares and initializes shell variables, but you can read
and modify them.  The BourneShell also initializes the read-only
shell variables, and you can read but not modify them.


2.1  User Variables


It is legal to assign any sequence of non-blank characters as the
name of a variable.  The sample session below creates a variable
called person and initializes it with the string Richard.
 
It is important to note that you must NOT precede or follow the
equal sign with a space or TAB character.

Sample Session:
                        
кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
Г  $person=Richard                                              Г
РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй
                                                                 

This sample session indicates that person does not represent the