C++ Tutorial/File Stream/file utilities
Версия от 14:21, 25 мая 2010; (обсуждение)
Содержание
- 1 A file comparision utility.
- 2 A simple file-comparison utility.
- 3 Check file status
- 4 Copying one file into another:
- 5 Count number of lines of all files passed as argument
- 6 Get file information: size, device, creation time and last modification time
- 7 Obtaining file size
- 8 Use ifstream and ofstream to copy file
A file comparision utility.
#include <iostream>
#include <fstream>
using namespace std;
int main(int argc, char *argv[])
{
register int i;
int numread;
unsigned char buf1[1024], buf2[1024];
ifstream f1("file1", ios::in | ios::binary);
if(!f1) {
cout << "Cannot open first file.\n";
return 1;
}
ifstream f2("file2", ios::in | ios::binary);
if(!f2) {
cout << "Cannot open second file.\n";
return 1;
}
do {
f1.read((char *) buf1, sizeof buf1);
f2.read((char *) buf2, sizeof buf2);
if(f1.gcount() != f2.gcount()) {
cout << "Files are of differing sizes.\n";
f1.close();
f2.close();
return 0;
}
for(i=0; i<f1.gcount(); i++) {
if(buf1[i] != buf2[i]) {
cout << "Files differ.\n";
f1.close();
f2.close();
return 0;
}
}
} while(!f1.eof() && !f2.eof());
cout << "Files are the same.\n";
f1.close();
f2.close();
return 0;
}Cannot open first file.
A simple file-comparison utility.
#include <iostream>
#include <fstream>
using namespace std;
int main(int argc, char *argv[])
{
bool equal = true;
bool ferr = false;
unsigned char buf1[1024], buf2[1024];
if(argc!=3) {
cout << "Usage: compfiles <file1> <file2>\n";
return 1;
}
ifstream f1(argv[1], ios::in | ios::binary);
if(!f1) {
cout << "Cannot open " << argv[1] << endl;
return 1;
}
ifstream f2(argv[2], ios::in | ios::binary);
if(!f2) {
cout << "Cannot open " << argv[2] << endl;
f1.close();
if(!f1.good())
cout << "Error closing " << argv[1] << endl;
return 1;
}
do {
f1.read((char *) buf1, sizeof buf1);
f2.read((char *) buf2, sizeof buf2);
if(!f1.eof() && !f1.good()) {
cout << "Error reading " << argv[1] << endl;
ferr = true;
break;
}
if(!f2.eof() && !f2.good()) {
cout << "Error reading " << argv[2] << endl;
ferr = true;
break;
}
if(f1.gcount() != f2.gcount()) {
cout << "Files are different lengths.\n";
equal = false;
break;
}
for(int i=0; i < f1.gcount(); ++i)
if(buf1[i] != buf2[i]) {
cout << "Files differ.\n";
equal = false;
break;
}
} while(!f1.eof() && !f2.eof() && equal);
if(!ferr && equal) cout << "Files are the same.\n";
f1.clear();
f2.clear();
f1.close();
f2.close();
if(!f1.good() || !f2.good()) {
cout << "Error closing files.\n";
return 1;
}
return 0;
}Check file status
#include <iostream>
#include <fstream>
using namespace std;
void checkstatus(ifstream &in);
int main(int argc, char *argv[])
{
ifstream in("test.txt");
char c;
while(in.get(c)) {
checkstatus(in);
}
checkstatus(in); // check final status
in.close();
return 0;
}
void checkstatus(ifstream &in)
{
ios::iostate i;
i = in.rdstate();
if(i & ios::eofbit)
cout << "EOF encountered\n";
else if(i & ios::failbit)
cout << "Non-Fatal I/O error\n";
else if(i & ios::badbit)
cout << "Fatal I/O error\n";
}EOF encountered
Copying one file into another:
#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
void print_error(const char*, const char* = " ");
int main(int argc, char* argv[])
{
if (3 != argc)
print_error("usage: copy source dest");
ifstream in( argv[1], ios::binary );
if (!in)
print_error( "can"t open", argv[1] );
ofstream out( argv[2], ios::binary );
if (!out)
print_error( "can"t open", argv[2] );
char ch;
while ( in.get(ch) )
out.put( ch );
if ( !in.eof() )
print_error("something strange happened");
return 0;
}
void print_error(const char* p, const char* p2) {
cerr << p << " " << p2 << "\n";
exit(1);
}Count number of lines of all files passed as argument
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iterator>
#include <algorithm>
#include <fstream>
#include <iostream>
int countLines (std::istream& in);
int main (int argc, char* argv[])
{
int count;
if (argc == 1) {
// no argument => count lines of standard input
count = countLines(std::cin);
}
else {
// count number of lines of all files passed as argument
std::ifstream in;
count = 0;
for (int i=1; i<argc; ++i) {
in.open(argv[i]);
if (!in) {
std::cerr << "failed to open " << argv[1] << "\n";
}
else {
count += countLines(in);
in.close();
}
}
}
std::cout << count << std::endl;
}
int countLines (std::istream& in)
{
return std::count(std::istreambuf_iterator<char>(in),
std::istreambuf_iterator<char>(),
"\n");
}asdf ^CTerminate batch job (Y/N)? n
Get file information: size, device, creation time and last modification time
#include <iostream>
#include <ctime>
#include <sys/types.h>
#include <sys/stat.h>
#include <cerrno>
#include <cstring>
int main(int argc, char** argv )
{
struct stat fileInfo;
if (stat("test.txt", &fileInfo) != 0) { // Use stat( ) to get the info
std::cerr << "Error: " << strerror(errno) << "\n";
return(EXIT_FAILURE);
}
std::cout << "Type: : ";
if ((fileInfo.st_mode & S_IFMT) == S_IFDIR) { // From sys/types.h
std::cout << "Directory\n";
} else {
std::cout << "File\n";
}
std::cout << "Size : " <<
fileInfo.st_size << "\n"; // Size in bytes
std::cout << "Device : " <<
(char)(fileInfo.st_dev + "A") << "\n"; // Device number
std::cout << "Created : " <<
std::ctime(&fileInfo.st_ctime); // Creation time
std::cout << "Modified : " <<
std::ctime(&fileInfo.st_mtime); // Last mod time
}Type: : File Size : 21 Device : C Created : Mon Apr 23 11:16:57 2007 Modified : Mon Apr 23 13:09:24 2007
Obtaining file size
#include <iostream.h>
#include <fstream.h>
const char * filename = "test.txt";
int main () {
long l,m;
ifstream file (filename, ios::in|ios::binary);
l = file.tellg();
file.seekg (0, ios::end);
m = file.tellg();
file.close();
cout << "size of " << filename;
cout << " is " << (m-l) << " bytes.\n";
return 0;
}size of test.txt is 40 bytes.
Use ifstream and ofstream to copy file
#include <iostream.h>
#include <fstream.H>
main(void)
{
char ch;
ifstream f1("test.txt");
ofstream f2("text1.txt");
if(!f1)
cerr <<"Can"t open IN file\n";
if(!f2)
cerr << "Can"t open OUT file\n";
while(f1 && f1.get(ch) )
f2.put(ch);
return (0);
}