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tail2.cc
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tail2.cc
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// tail2.cc
// IJC-DU2
// Author: Miroslav Karásek, FIT
// Date: 2015-04-18
#include <iostream>
#include <string>
#include <fstream>
#include <queue>
typedef struct {
bool is_help;
bool is_from;
unsigned long count;
const char *filename;
} args_t;
void print_help()
{
std::cout <<
"Usage:\n"
" tail [ARGUMENTS] [FILE]\n"
"\n"
"Arguments:\n"
" -h print help\n"
" -n COUNT specifics number of last lines \n"
" -n +COUNT specifics first line to write\n"
" default argument is -n 10\n"
"\n"
"File:\n"
" if not set it will be use standard input\n";
}
void get_args(args_t &args, int argc, const char **argv)
{
using namespace std;
const char *number_argument = NULL;
for (int i = 1; i < argc; i++)
{
string argument(argv[i]);
if (argv[i][0] == '-')
{
if (argv[i][1] == 'n')
{
if (number_argument)
{
cerr << "More -n parameters" << endl;
throw 1;
}
if (argv[i][2] == '\0')
i++;
else
argv[i] += 2;
if (i < argc)
number_argument = argv[i];
else
{
cerr << "After -n must be count" << endl;
throw 2;
}
}
else if (argument == "-h" || argument == "--help")
{
args.is_help = true;
}
else
{
cerr << "Unknown argument " << argv[i] << endl;
throw 3;
}
}
else
{
if (args.filename)
{
cerr << "More files specified" << endl;
throw 4;
}
args.filename = argv[i];
}
}
if (number_argument != NULL)
{
char *ptr;
args.count = strtol(number_argument, &ptr, 0);
if (ptr[0] == '\0')
{
if (number_argument[0] == '+')
args.is_from = true;
else
args.is_from = false;
}
else
{
cerr << "Bad format after -n" << endl;
throw 5;
}
}
}
int main(int argc, char const *argv[])
{
using namespace std;
args_t args {false, false, 10, NULL};
ifstream input;
try
{
get_args(args, argc, argv);
}
catch (int e)
{
cerr << "Use -h or --help for help" << endl;
return e;
}
if (args.is_help)
{
print_help();
return 0;
}
if (args.filename)
{
input.open(args.filename, ios::in);
if (!input.is_open())
{
cerr << "File " << args.filename << " can not be opened" << endl;
return 1;
}
cin.rdbuf(input.rdbuf());
}
if (args.is_from)
{
string line;
for(unsigned long i = 1; getline(cin, line); i++)
{
if (i >= args.count)
{
cout << line << endl;
}
}
}
else
{
queue<string> buffer;
string line;
for(unsigned long i = 0; getline(cin, line); i++)
{
buffer.push(line);
if (i >= args.count)
buffer.pop();
}
while (!buffer.empty())
{
cout << buffer.front() << endl;
buffer.pop();
}
}
input.close();
return 0;
}