More on shells
Overview
Simple arithmetic
Arithmetic
expansion
Operators for arithmetic
expansion
The 'expr'
command
Pattern matching
Patterns
Examples of patterns
The case
statement
Entering and leaving the
shell
More about scripts with
options
Symbolic
links
Setting up terminals
Conventions used in
UNIX file systems
Summary
Exercises
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Exercises
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Write a script cm2ftin which uses arithmetic
expansion to convert from centimetres to feet and inches, rounded
down to the nearest whole number of inches. Input should be a whole
number of centimetres, and you may assume 1 foot is 30 cm.
$ cm2ftin
Enter cm: 42
42 cm is 1 foot 5 inches
View solution
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Repeat exercise 1 using expr instead of arithmetic
expansion.
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Write a script to read a single argument, representing the name
of a text file, and display the average number of characters per
line (excluding Newline characters) to two decimal places.
Make sure that the script can handle the cases when it is called
with the wrong number of arguments and when it cannot access the
required file. Hint: use read and
wc.
View solution
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Write a script called area to take two numerical
arguments, representing the base length and height of a
right-angled triangle, plus one or two options -a and
-h (meaning area and help). With
option -a, the area of the triangle should be
displayed on standard output preceded by the message Area
is, and with option -h a short help message
should be displayed. With no options, there should be no output;
any other option should be ignored, except that a warning message
should be output on standard error.
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Write a script called hello to display one of
Good morning, Good afternoon or
Good evening depending on the time of day. You should
use the output of date and pattern matching.
View solution
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Write a script called saytime to display the
current time in words.
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Write a script called drawsquare to take as
argument a single number, between 3 and 15 inclusive, and draw on
the standard output a square, using the symbols +
(plus), - (hyphen) and | (vertical bar),
so:
$ drawsquare 4
+--+
| |
| |
+--+
If drawsquare is presented without arguments, with more than 1
argument, or with a single argument that is not a number between 3
and 15, it should display an error message and exit with status
1.
View solution
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Write a script called drawcube to take as argument
a single number, between 3 and 15 inclusive, and draw on the
standard output a cube, using the symbols + (plus),
- (hyphen), / (slash) and |
(vertical bar), so:
$ drawcube 4
+--+
/ /|
/ / |
+--+ +
| | /
| |/
+--+
If drawcube is presented without arguments, with
more than 1 argument, or with a single argument that is not a
number between 3 and 15, it should output an error message and exit
with status 1.
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Write a script called eurhello to display a
greeting in one of several languages. With option -e,
or with no options, eurhello should use the greeting
Hello, with option -f it should use the
French Bonjour, and with option -g it
should use the German Guten Tag. It should also allow
an option -G, which takes an argument, allowing an
arbitrary greeting. Following any options, an argument, which is a
string representing the name of the person to whom the greeting is
addressed, is required:
$ eurhello Chris
Hello Chris
$ eurhello -f "Monsieur le President"
Bonjour Monsieur le President
$ eurhello -G "Hi there" Sam
Hi there Sam
If several of the three possible options are given as arguments
to the script, the last (rightmost) one takes precedence.
View solution
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