Program 4a: getopt() Solution



  • Goals

    1. To develop a command language for DiskSweeper.

    1. To use getopt() to process single-letter options.

    1. To build the rst phase of the DiskSweeper application.

    1. To learn or review some parts of C++ that will be needed in this course.

  • The Project

The Disk Sweeper application will search your hard disk for les that are copies of each other and report the full pathnames of all copies of the le. The command name will be sweep. The arguments will be:

-o lename (required): open and use the named le for output.

-v (optional): provide verbose debugging feedback.

-d (optional): delete all duplicates except the rst.

A small integer (optional): a minimum le size to work on, in kilobytes. (That is, 5 represents 5K bytes.)

A pathname (a string, required): the directory at which to start sweeping.

In stage 4b of this program, we will add some long switches.

  • Instructions

Write a program to parse the command line for DiskSweeper. Due Sept. 22 (Friday).

De ne a class named Params. Members of the class should include:

An ofstream.

The pathname of the starting directory, a C-style string.

An integer: the minimum size le to process. The default should be 0 for this optional parameter.

A boolean variable for each switch. (All are optional, the defaults are all false.)

The Params constructor should have two parameters: argc and argv. Process the command-line arguments using getopt() (instructions follow) and initialize the data members to the settings that you nd on the command line. Open the ofstream for output to the le named on the command line.

print( ): print all the members except the stream in a nice format to the open ofstream.

In your main function, declare an instance of Params and pass argc and argv to its constructor.

When construction is nished, call Params::print() to display the params.

Program 4a: getopt() CSCI 4547 / 6647 Systems Programming 2

  • Using getopt() to Decode Command-line Arguments

The function getopt() automates and vastly simpli es the process of decoding a command line. The example shown here is NOT what you need for your project; it is provided only so that you can understand the syntax of the getopt() function.

Syntax: int = getopt( int argc, char* argv[], const char* opts );


for (;;) f

ch = getopt(argc, argv, “i:avRou”);

if( ch == -1 ) break;

switch( ch )f

. . .

argc and argv are the parameters received from the shell by your program.

opts is a string containing all the short switch options that your program supports: “i:avRou” This string of letters means that the application will accept the switches i, a, v, R, o, u. A command line could give any combination of switches, in any order.

An option letter followed by a colon requires a parameter (usually a le name). In this example, the -i switch must be followed by the name of an input le.

An option letter followed by a double colon has an optional parameter (no example here).

Processing the switches. Your program must use getopt() in a loop, as shown, to read and validate the switches that are present and store that information in Param’s variables. Print a usage comment after any error you discover. Getopt returns -1 when there are no more switches to process.

Processing the required arguments. After returning from getopt(), set a local variable, required = optind. Optind is a global variable, so this should be done immediately. The number is the subscript of the rst non-switch argument on the command line, and the rst thing you must process after returning from getopt().

Since there is only one required argument in DiskSweeper, required should be argc-1. If this is not true, print a usage error comment.

Set your path, equal to the required pathname.

Finishing up. After processing the command-line arguments, print a report like the one shown below and end. Test all of the command-line options and capture the results from all tests in one le, using append mode. Here is some sample output:

Command: sweep -v -o dupfiles.txt 10 ~/A_UNH/Teaching

Verbose? Yes

Delete? No

Output file name: dupfiles.txt

Size: 10 K or greater

Directory: ~/A_UNH/Teaching

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