commandline.cpp

C++ PRIME书中的原代码,看本书时可以学习的例子.

// Section 7.8
// $ CC commandline.cpp

/* output:
 a.out -d -l 1024 -o test_7_8 chapter7.doc chapter8.doc
illustration of handling command line arguments:
argc: 8
argv[ 1 ]: -d
case '-' found
-d found: debugging turned on
argv[ 2 ]: -l
case '-' found
-l found: resource limit
argv[ 3 ]: 1024
default non-hypen argument: 1024
argv[ 4 ]: -o
case '-' found
-o found: output file
argv[ 5 ]: test_7_8
default non-hypen argument: test_7_8
argv[ 6 ]: chapter7.doc
default non-hypen argument: chapter7.doc
argv[ 7 ]: chapter8.doc
default non-hypen argument: chapter8.doc
User-specifed limit: 1024
User-specified output file: test_7_8
Files to be processed are the following:
        chapter7.doc
        chapter8.doc
*/

#include <iostream>
using std::cerr;
using std::cout;
using std::endl;

#include <cstdlib>
using std::exit;

#include <string>
using std::string;

#include <vector>
using std::vector;

#include <ctype.h>

const char *const program_name = "comline";
const char *const program_version = "version 0.01 (08/07/97)";

inline void usage( int exit_value = 0 )
{
	// prints out a formatted usage message,
	// and exits using the exit_value ...

	cerr << "usage:\n"
	     << program_name << " "
	     << "[-d] [-h] [-v] \n\t"
	     << "[-o output_file] [-l limit] \n\t"
	     << "file_name\n\t[file_name [file_name [ ... ]]]\n\n"
	     << "where [] indicates optional option:\n\n\t"
	     << "-h: help.\n\t\t"
	     << "generates this message and exits\n\n\t"
	     << "-v: version.\n\t\t"
	     << "prints version information and exits\n\n\t"
	     << "-d: debug.\n\t\tturns debugging on\n\n\t"
	     << "-l limit\n\t\t"
	     << "limit must be a non-negative integer\n\n\t"
	     << "-o ofile\n\t\t"
	     << "file within which to write out results\n\t\t"
	     << "by default, results written to standard output\n\n"
	     << "file_name\n\t\t"
	     << "the name of the actual file to process\n\t\t"
	     << "at least one file_name is required --\n\t\t"
	     << "any number may be specified\n\n"
	     << "examples:\n\t\t"
	     << "$command chapter7.doc\n\t\t"
	     << "$command -d -l 1024 -o test_7_8 "
	     << "chapter7.doc chapter8.doc\n\n";

	exit( exit_value );
}

int main( int argc, char* argv[] )
{
	bool debug_on = false;
	bool ofile_on = false;
	bool limit_on = false;
	int limit = -1;

	string ofile;
	vector<string> file_names;

	cout << "illustration of handling command line arguments:\n"
	     << "argc: " << argc << endl;

	for ( int ix = 1; ix < argc; ++ix ) 
	{
		cout << "argv[ " << ix << " ]: " 
		     << argv[ ix ] << endl;

		char *pchar = argv[ ix ];
		switch ( pchar[ 0 ] ) 
		{
			case '-':
			{
				cout << "case \'-\' found\n"; 
				switch( pchar[ 1 ] ) 
				{
					case 'd':
						cout << "-d found: "
						     << "debugging turned on\n";

						debug_on = true;
						break;

					case 'v':
						cout << "-v found: "
						     << "version info displayed\n";

						cout << program_name
						     << " ::  " 
						     << program_version
						     << endl;

						return 0;

					case 'h':
						cout << "-h found: "
						     << "help information\n";

						// no break necessary: usage() exits
						usage();

					case 'o':
						cout << "-o found: output file\n";
						ofile_on = true;
						break;

					case 'l':
						cout << "-l found: "
						     << "resource limit\n";

						limit_on = true;
						break;

					default:
						cerr << program_name 
						     << " : error : "
						     << "unrecognized option: - "
						     << pchar << "\n\n";

						// no break necessary: usage() exits
						usage( -1 );
				}
				break;
			}

			default: // either a file name
				cout << "default nonhyphen argument: "
				     << pchar << endl;

				if ( ofile_on ) {
					ofile_on = false;
					ofile = pchar;
				}
				else 
				if ( limit_on ) {
					limit_on = false;
					limit = atoi( pchar );
					if ( limit < 0 ) {
						cerr << program_name
						     << " : error : "
						     << "negative value for limit.\n\n";

						usage( -2 );
					}
				}
				else file_names.push_back( string( pchar ));
				break;
		}
	}

	if ( file_names.empty() ) {
		cerr << program_name 
		     << " : error : "
		     << "no file specified for processing.\n\n";

		usage( -3 );
	}

	if ( limit != -1 ) 
		cout << "User-specifed limit: "
		     << limit << endl;

	if ( ! ofile.empty() )
		cout << "User-specified output file: "
		     << ofile << endl;

	cout << (file_names.size() == 1 ? "File " : "Files ")
	     << "to be processed are the following:\n";	

	for ( int inx = 0; inx < file_names.size(); ++inx )
		cout << "\t" << file_names[ inx ] << endl;
}