CSE 190 Sp 2000 -- Assignment 3 -- May 18, 2000

Sample Solutions

rev_args.sh -- bourne shell version
rev_args_bash.sh -- bash version
rev_args.ksh -- ksh version

A Simple Shell Script

Write a shell script rev_args that performs the following:

output its arguments in reverse order:

$ rev_args arg1 'argument two' arg3
arg3 argument two arg1
$

accepts a -q flag to generate quoted output:

$ ./rev_args -q "multi word arg" hi there "'tis good"
''"'"'tis good' 'there' 'hi' 'multi word arg'
$

with the appropriate quoting so that the output can be passed to the following showargs script new!

$ cat ~/bin/showargs
#!/bin/sh
echo "There are $# args"
for i
do
        printf '%s\n' "$i"
done
$

by an eval:

$ eval ./showargs $(./rev_args -q "multi word arg" hi there "'tis good")
There are 4 args
'tis good
there
hi
multi word arg
$

(Note that the $(...) construct is the same as the backquote that I mentioned in class. The $(...) construct is a bash extension, which makes nesting of backquoted commands easier.)

You may do this assignment using either the Bourne shell (e.g. /bin/sh), bash, or ksh.

Hints

To do the substitution for the single quotes, usually echo and sed are used. You should probably look at printf(1) as well.

Good test cases:

$ ./rev_args.sh -q "'tis a cruel world" "ain't it?" sure thang -n
'-n' 'thang' 'sure' 'ain'"'"'t it?' ''"'"'tis a cruel world' 
$ ./rev_args.sh "'tis a cruel world" "ain't it?" sure thang -n
-n thang sure ain't it? 'tis a cruel world
$ ./rev_args.sh -q -- -q -n -q -n
'-n' '-q' '-n' '-q' 
$ ./rev_args.ksh -- sometimes -q means just -q
-q just means -q sometimes

Note: I did not ask for you to implement the common idiom of using "--" to indicate the end of command flags processing. You don't have to implement it, but it is a good idea. Without it, there is no way to do the following:

$ ./rev_args.sh -- -q means quoting
quoting means -q
$

Also, think about the difference between the following two commands:

$ eval ./showargs `./rev_args.sh -q "'tis a shame" foo bar "ain't so   hard"`
There are 4 args
ain't so hard
bar
foo
'tis a shame
$ eval ./showargs "`./rev_args.sh -q "'tis a shame" foo bar "ain't so   hard"`"
There are 4 args
ain't so   hard
bar
foo
'tis a shame
$

Grades

The grades statistics are:

38 students handed in assignment 3.

assignment 3 as a whole: mean  75.2368
                         stdev 28.5615

w/o late adjustment: mean  75.2368
                     stdev 28.5615

Excluding all-zero scores:

assignment 3 as a whole: mean  81.6857
                         stdev 18.9447

w/o late adjustment: mean  81.6857
                     stdev 18.9447

Per-problem statistics:

Num  1:  mean  9.026316
         stdev 2.869869
Num  2:  mean  7.000000
         stdev 4.198997
Num  3:  mean  7.947368
         stdev 3.986473
Num  4:  mean  5.447368
         stdev 3.904770
Num  5:  mean  6.421053
         stdev 4.705157
Num  6:  mean  9.000000
         stdev 2.928984
Num  7:  mean  7.684211
         stdev 3.907518
Num  8:  mean  7.736842
         stdev 3.843547
Num  9:  mean  8.578947
         stdev 3.305749
Num 10:  mean  6.394737
         stdev 4.088105


Per-problem statistics, omitting zero grades:

Num  1:  mean  9.800000
         stdev 1.166190
Num  2:  mean  8.060606
         stdev 3.428397
Num  3:  mean  9.741935
         stdev 1.413478
Num  4:  mean  6.088235
         stdev 3.624814
Num  5:  mean  9.384615
         stdev 2.131755
Num  6:  mean  9.771429
         stdev 1.332789
Num  7:  mean  8.588235
         stdev 3.049760
Num  8:  mean  8.647059
         stdev 2.939411
Num  9:  mean  9.314286
         stdev 2.239533
Num 10:  mean  6.942857
         stdev 3.786765

The grade distribution is:
grade distribution bar graph

The test cases and the program used to test your script can be found in /home/solaris/ieng9/cs190e/public/assn3/

bsy+cse190.s00@cs.ucsd.edu, last updated Tue May 30 18:54:58 PDT 2000. Copyright 2000 Bennet Yee.
email bsy.