Homework / Exams

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 Exam3

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 ux 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
• _at_ 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
• same as above
• 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
• _at_ a a b
• if (a gt 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 ltSTDINgt)
• 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, ltSTDINgt line 1.

16
Review for Exam 3

• The floor is now open for questions