Description
1. Overview
In this assignment, you will learn how to access files, and make use of command line arguments by
writing a utility similar to the program fmt(1). Read the man page for fmt by typeing the command :
man -s 1 fmt
Whenever you see the name of a command in bold face followed by a number in parentheses, it refers
to a command in a certain section of the Unix man pages. In this case, section 1 contains the documentation for the program fmt. Your program will be similar but not identical. Follow the specification given here. There is also a reference implementation written in Perl (misc/pfmt.perl).
2. Program Specification
We present the program specification in the form of a Unix man(1) page.
NAME
jfmt — simple text formatter
SYNOPSIS
jfmt [−width] [filename …]
DESCRIPTION
The format utility reads in text lines from all of its input files and writes its output to stdout.
Error messages are written to stderr. Each file is handled separately, and within each file, all
consecutive sequences of lines containing non-whitespace characters are considered as a single
paragraph. A paragraph is written out with a maximal sequence of words not to exceed the
specified output line width. It is then followed by one empty line.
OPTIONS
-width
The specified width is the maximum number of characters in an output line. Ifaword
that is longer than width is found, it is printed on a line by itself. The default width is 65
characters.
OPERANDS
Each operand is a file name, and they are read in sequence. An option is recognized as such
only if it begins with a minus sign and precedes all operands. If any operand is specified as a
single minus sign (-), then stdin is read at that point.
EXIT STATUS
0 All files were read successfully, output was sucessfully generated, and no errors were
detected.
1 Errors were detected and messages were written to stderr.
SEE ALSO
fmt(1), pfmt.perl.
3. Implementation Sequence
Whenever your write a program that is non-trivial, you should follow some iplementation sequence
that develops a program a little bit at a time, keeping a working program and adding to it little by
little. Make backups frequently.
(1) Start with the given code : The code/ subdirectory contains some starter code for yor project.
The misc/ subdirectory contains some examples you should study, but which are not directly
useable in your code.
CMPS-012B • Fall 2013 • Assignment 1 • Format utility, files, args page 2 of 3
(2) Make sure checksource and cid are in your $PATH environment variable. The first checks on
basic formatting, and the second will check your code into an RCS archive.
(3) Play around with pfmt.perl to see what your program should do. If you copy this file into your
development directory, make sure the x-bit is on.
(4) The program jfmt.java, as given, merely cycles through the files and prints debug code. Each
line is printed as it is read, and each word within that line is read. Note that words are
selected from a line with a white space regular expression passed to split. “\\s+” is a string
representing the regular expression \s+, which matches any sequence of white space.
(5) As you are developing Java code, you should have your browser pointed at
http://docs.oracle.com/javase/7/docs/api/index.html,
which is the Java™ Platform, Standard Edition 7 API Specification.
(6) Your program should have the following import statements at the beginning :
import java.io.*;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;
import static java.lang.System.*;
Important note : In this assignment, you may use anything in java.util, but in general in this
course you are prohibited from using anything from that package except when explicitly authorized. See the syllabus for a list of classes in java.util that you may always use.
(7) Read about interface java.util.List and class java.util.LinkedList. Then, at the beginning of
the function format, add in the following declaration :
List words = new LinkedList();
Delete the line that echos input lines and instead of printing the words found in each line, add
them to the list of words. Note that you need to take special care not to add an empty leading
word to the list of words. (What does split do when there is a space ahead of the first word ?)
(8) Create a function print_paragraph which is called whenever you see the end of a paragraph.
This function removes and prints each word in the list. The end of a paragraph occurs at end of
file. It also occurs with an empty line, i.e., a line that contains only spaces and tabs or nothing
at all. Sequences of empty lines produce the same output as a single empty line.
(9) Look at interface java.util.Iterator. The function print_paragraph should create an iterator
over the list :
for (String word: words)
As you iterate over each word, print it, with a space between words, but not before the first
word, nor after the last word of the line. Whenever printing a word would exceed the line
length, print a newline character. Note that the first word on a line is printed whether or not it
exceeds the line length.
(10) When you are finished with the list, empty it :
words.clear();
(11) An alternative method is to create a StringBuffer to accumulate words until the line is full. In
this case, don’t use string concatenation (+). Use StringBuffer . append. This is what the inner
loop of the Perl code does. Study it an duplicate its functionality. Use diff(1) to check the output of your program against that of pfmt.perl.
(12) Add code to examine args to see if there is a maximum line length parameter, and if so, keep it
in a variable. If args[0] exists, it is a valid option if args[0] . matches (“−\\d+”), an invalid
option if args[0] . matches (“− . +”), and otherwise not an option at all.
(13) A string may be converted to an integer by using Integer.parseInt (see the Java 1.5 API documentation for java.lang.Integer). You can either use substring to ignore the minus sign, or
negate the result after conversion. Note that any word from the command line that
equals (“−”) is not an option, but an operand. Instead of bothering to check for formatting
CMPS-012B • Fall 2013 • Assignment 1 • Format utility, files, args page 3 of 3
using the matches function in the previous point, You could just assume it is valid, but use a
try-catch construct to catch a NumberFormatException if not.
4. Program Testing
It is extremely important to test your program and verify that it works under all possible circumstances. The subdirectory .score contains some files : SCORE is the grader’s score sheet, to be used to
evaluate your program. After submitting your code, run testsubmit and then cd into the directory.
Copy the files mk.build and mk.test and run them to verify that your program works.
To see exactly what testing should look like, copy the input files into your baseline directory (separate from your development directory), make a symbolic link to make jfmt point at pfmt.perl and see
what output the Perl program produces. Your output should be identical, including stdin, stdout,
and the exit status.
5. What to Submit
Submit the files README, Makefile, jfmt.java. If you are doing pair programming, be sure to edit your
README, as required in the pair programming directory, and add the PARTNER file to your submit list.
Verify the submit ! This is explained in lab1. If you don’t submit all of the necessary code, you will
lose many points. Do not submit the jar file or any class files. Make sure your Makefile works. Do a
pre-grade using the information in the .score subdirectory.
