First:

Login to your Unix account and type:

% /home/cs476/mlist

To put your login name in cs476 mailing list.

Introduction to UNIX

à Dot files:

To change the behavior of programs.

Examples: .login, .cshrc, .mailrc, .forward, etc...

à Unix Man pages:

Extensive on-line documentation.

Examples: man, info, apropos, whereis, which, etc..

à Editing:

You may use any program to edit a file.

Examples: vi, emacs. ed, MS word, notebad, etc...

à Program Management:

v Makefile:

hello : hello.o PrintDate.o

<tab> gcc -o hello hello.o PrintDate.o

hello.o : hello.c

<tab> gcc -c hello.c

PrintDate.o : PrintDate.c

<tab> gcc -c PrintDate.c

clean:

<tab> rm *.o hello

hello.c:

main()

{

printf("Hello World\n");

PrintDate();

}

PrintDate.c:

void PrintDate()

{

system("date");

}

% make /* produce hello */

% make clean /* removes *.o and hello */

v Archive:

% tar cf hello.tar * /* create */

% tar tf hello.tar /* list */

% tar xf hello.tar /* extract */

% gzip hello.tar /* compress*/

% gunzip hello.tar.gz /* uncompress */

v Libraries:

PrintDate.c:

void PrintDate()

{

system("date");

}

Math.c:

char *compare(int i1, int i2)

{

if (i1 > i2) return "first";

else if (i2 > i1) return "second";

else return "equal";

}

int diff (int i1, int i2)

{

return (i1-i2);

}

int sum (int i1, int i2)

{

return (i1+i2);

}

Makefile:

OBJ= PrintDate.o Math.o

all: $(OBJ) libcs476.a

PrintDate.o : PrintDate.c

gcc -c PrintDate.c

Math.o : Math.c

gcc -c Math.c

libcs476.a : $(OBJ)

ar r libcs476.a $(OBJ)

clean:

rm *.o libcs476.a

libcs476.h:

void PrintDate();

char *compare(int, int);

int sum(int, int);

To list the contents of the library:

% ar t libcs476.a

Example to use the library:

testlibcs476.c:

#include <stdio.h>

#include "libcs476.h"

int main()

{

PrintDate();

printf("%s\n",compare(13, 27));

printf("%d\n", diff (13, 27));

printf("%d\n", sum (13, 27));

}

Makefile:

testlibcs476 : testlibcs476.c

gcc -o testlibcs476 testlibcs476.c -lcs476 -L.

clean:

rm testlibcs476

à Unix file system:

% ls -l
- rwx rwx rwx 2 wahab  faculty   1278   Aug 25   file1

% touch

Example:

% mkdir test
         % cd test

          % touch file
          % ls -l

                                 -rw-------   1 wahab    faculty         0 Aug  1 23:25 file

% /usr/bin/touch 1226112272 file
% ls -l

                                 -rw-------   1 wahab    faculty         0 Dec 26  1972 file

% stat file

/* all details about the file */

…….

Modify: 1972-12-26 11:22:00

…….

  % find

Example :

Remove all files under directory test named
a.out  or *.o    that have not been accessed for a week:

% find ./test \( -name a.out -o -name '*.o' \)
-atime +7 -exec rm {} \;

% chmod -R a+rx *

  % cp -r path1 path2

  % rm -r path

à The cat & tail story:

Creating the world's first chat!

% cat >> /tmp/wahab
% tail -f /tmp/Wahab

à Which Shell?

% sh (Bourne shell, the oldest shell)

% bash (Bourne-again shell, a super set of sh)

% csh (Berkeley, syntax resembles C language)
% tcsh (derivative of csh)
% ksh (korn shell-the newest shell)

à All Shells has:

|     >     >>     <    &

E.g. % ls -lt | more

Eample 1: Producing pdf version of  a man page:

% whereis touch

touch: /usr/bin/touch /usr/ucb/touch /usr/local/bin/touch /usr/man/man1/touch.1 /usr/man/man1b/touch.1b

% troff -man /usr/man/man1/touch.1 > t1
% dpost t1 > t2
% ps2pdf t2  touch.pdf

OR combine all the above  commands using | as:

% troff -man /usr/man/man1/touch.1 | dpost | ps2pdf – touch.pdf

Eample 2:

% cb < prog.c > prog.b

         % more prog.b
         % mv prog.b prog.c

What will happen when you do:
% cb < prog.c > prog.c ???

We may combine all the above commands using | as:
         % cat prog.c | cb | tee prog.b

You can use instead of cb:

% indent prog.c

Eample 3:

% echo hi   > tmp
           % tail –f tmp >> tmp &

% tail –f tmp

à Some Shells (e.g. csh) has:

Job control

% sort bigfile1 > bigfile2
^Z

% jobs
.......  list of background jobs  ...........

     % kill -9 %job

     % ps
.........  list  of processes  ..................

     % kill -9 process

We can also use:

% pgrep <name>

% pkill <name>

à Quoting:

\C  , '......'  ,   `.......`  ,  " ....."

% echo *

             % echo \*                        quote ONE char

             % echo ' ***><? ' qoute ANY number of chars

             % mail ` cat list ` < letter  command substitution

             % echo " ` pwd ` $home " does not qoute ` ... `  and  $

à Shell and Environmnet Variables:

bourne shell:

$ path=.:/bin:/usr/bin    path is a standard shell variable
     $ echo $path
     $ d=`pwd`                    d is a user defined shell variable
$ echo $d

Note: there should be no spaces around =

csh shell:

% set path = .:/bin:/usr/bin
     % set d   =   `pwd`

% echo $d

     % setenv DISPLAY dogwood.cs.odu.edu:0
     % echo $DISPLAY

Environment variables:
            are automatically exported to all child processes.

Shell varibales:
            has to be explicitly exported.

Example:

     % set x=`pwd`
     % setenv y `pwd`
     % echo $x $y
     % csh
     % echo $x $y     x is undefined but y is defined.

à Bit-level operations:

You may access individual bits of any byte.

Example: bits

char B=0;

int i;

B=B | (1<<4) ; /*set 4th bit*/

printf("%d ", (B&(1<<i))>>i) ; /* print ith bit */

B=B & (~(1<<4)) ; /*clear 4th bit*/

à Debgging:

You may use any debugger to debug a program.

Example: gdb

Using –g flag to debug prog:

% gcc –g –o prog prog.c

Some gdp commands:

run, list, break <n>, clear <n>, display <var>, next, continue, quit