C++/File/File Status
Содержание
Check file status
#include <iostream>
#include <fstream>
using namespace std;
void checkstatus(ifstream &in);
int main(int argc, char *argv[])
{
if(argc!=2) {
cout << "Usage: DISPLAY <filename>\n";
return 1;
}
ifstream in(argv[1]);
if(!in) {
cout << "Cannot open input file.\n";
return 1;
}
char c;
while(in.get(c)) {
cout << 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";
}
End of file sign
#include <iostream>
#include <fstream>
using namespace std;
int main(int argc, char *argv[])
{
char ch;
if(argc!=2) {
cout << "PR: <filename>\n";
return 1;
}
ifstream in(argv[1]);
if(!in) {
cout << "Cannot open input file.\n";
return 1;
}
while(!in.eof()) {
in.get(ch);
// check for error
if(!in.good() && !in.eof()) {
cout << "I/O Error...terminating\n";
return 1;
}
cout << ch;
}
in.close();
return 0;
}
I/O Status
/*
Name Meaning
ios::goodbit No error bits set
ios::eofbit 1 when end-of-file is encountered; 0 otherwise
ios::failbit 1 when a (possibly) nonfatal I/O error has occurred; 0 otherwise
ios::badbit 1 when a fatal I/O error has occurred; 0 otherwise
*/
#include <iostream>
#include <fstream>
using namespace std;
void checkstatus(ifstream &in);
int main(int argc, char *argv[])
{
if(argc!=2) {
cout << "Usage: Display <filename>\n";
return 1;
}
ifstream in(argv[1]);
if(!in) {
cout << "Cannot open input file.\n";
return 1;
}
char c;
while(in.get(c)) {
if(in) cout << 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";
}
The string pointed to by mode determines how the file will be opened. The following table shows the legal values for mode. (Strings like ?+b?may also be represented as ?b+.?
Mode Meaning
r Open a text file for reading.
w Create a text file for writing.
a Append to a text file.
rb Open a binary file for reading.
wb Create a binary file for writing.
ab Append to a binary file.
r+ Open a text file for read/write.
w+ Create a text file for read/write.
a+ Append or create a text file for read/write.
r+b Open a binary file for read/write.
w+b Create a binary file for read/write.
a+b Append or create a binary file for read/write.