1. Homework / Exams HW7 due today Exam #3 next class
Covers Chapter 5 through end of Chapter 7
and Appendix B Standard Library
Plus UNIX Shells / Processes / Shell Scripts
Homework #8 due class 28
Review for Exam#3

2. Shell Scripts Yet another programming language! 
Save a sequence of UNIX commands in a file
Three different script languages with their own syntax – one for each type of UNIX shell! 
C shell script file names have suffix .csh
File permission for execute must be set
chmod u+x filename.csh
Then, type the filename at the UNIX prompt:
% filename.csh

3. C Shell Script Language
Builds on existing shell commands
Adds Expressions and Assignments
Adds comments, labels, and goto
Adds C-like Control Statements
foreach … end
if … then … else … endif
switch … case … endsw

4. C Shell Script Language
Assignment of expression value to variable
set a = 3
set b = 5
@ a = $a + $b
echo a = $a
Arithmetic only for integer variables

5. C Shell Script Language
Comment Syntax
# is start of a comment to end of line
# must be first character in file (for C shell script)
#!/bin/tcsh  Shebang gives path name to shell
Label Syntax
name: # Usually on a line by itself
goto Syntax
goto name

6. C Shell Script Language
Syntax for: foreach … end
foreach name (wordList)
… # use $name as loop variable
end

7. C Shell Script Language
Syntax for: if … then … else … endif
if (expr1) then
list 1 # shell commands
else if (expr2) then
list 2 # shell commands
else
list 3 # shell commands
endif

8. C Shell Script Language
Syntax for: switch … case … endsw
switch (expr)
case pattern1:
list # shell commands
breaksw # break out of this case
case pattern2:
… # same as above
default:
endsw

9. C Shell Script Example blade64(26)% pwd /home/bobw/cs240
blade64(27)% cat showhw.csh
# showhw.csh  AT LEAST 1 COMMENT LINE!
foreach subdir (hw1 hw2 hw3 hw4 hw5 hw6 hw7 hw8)
cd $subdir ls
cd ..
end

10. C Shell Script Example blade64(28)% showhw.csh soln
reverse.in soln trim.in vt.in
bits.c bits.h buggy.c showbits.c soln
makefile soln
explore.c soln
alloc.c alloc.h alloctest.c makefile soln test.in
makefile mapss.c mapss.h soln testmapss.c
differ.in1 differ.in2 soln

11. C Shell Script Example blade64(94)% cat foo.csh # set a = 3 set b = 5
@ a = $a + $b
if ($a > $b) then
echo $a is greater than $b
else
echo $a is not greater than $b
endif
blade64(95)% foo.csh
8 is greater than 5
blade64(96)%

12. AWK Programs Yet another programming language! 
Authors: Aho, Weinberger, and Kernighan
Invoke the awk utility with a program on a file
awk program defines operations to do on each line
blade64(43)% cat awk1
BEGIN { print "start of file: ", FILENAME}
{ print NF, $1}
END {print "end of file"}

13. AWK Programs blade64(44)% cat foo.txt Now is the time for all good men
to come to the aid
blade64(45)% awk -f awk1 foo.txt
start of file: foo.txt
4 Now
4 for
5 to
end of file

14. Perl Scripts Yet another programming language! 
Practical Extraction and Reporting Language
aka Pathologically Eclectic Rubbish Lister
Falls between a Shell script and a C program
Often used instead of shell scripts, awk, sed
There are a2p and s2p translators available
You can actually write O-O perl scripts!

15. Perl Scripts blade64(46)% cat test.pl print "What is your name? ";
chomp($name = <STDIN>);
$length = length $name;
($length == 3)? print "$name has $length characters.\n": die;
blade64(47)% perl test.pl
What is your name? Bob
Bob has 3 characters.
blade64(48)% perl test.pl
What is your name? Robert
Died at test.pl line 4, <STDIN> line 1.

16. Review for Exam #3
The floor is now open for questions