Removing "funny" characters from a file in C++ [closed] - c++

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I have a text file that consists of "funny" non-ASCII characters such as NUL, RS, CAN all in a black square. When I read the file line by line, it just stops each line where one of these appear.
All I want to do is to copy the same file only without these characters.
How to do that?

Answer 1

Let's say you are reading the file line by line and write the output to a different file like this:
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
int main() {
string inPath("a.txt");
string outPath("b.txt");
string line;
ifstream in(inPath.c_str(), ifstream::in | ifstream::binary);
if ( ! in.is_open() ) {
cerr << "Error: Failed to read file \"" << inPath << "\"." << endl;
return EXIT_FAILURE;
}
ofstream out(outPath.c_str(), ofstream::out | ofstream::binary);
if ( ! out.is_open() ) {
cerr << "Error: Failed to write file \"" << outPath << "\"." << endl;
return EXIT_FAILURE;
}
while ( getline(in, line) ) {
out << line;
}
cout << "Done." << endl;
return EXIT_SUCCESS;
}
The problem is that the input stream gets interpreted if not opened in binary mode. That means all control characters (the ones you see in Notepad++ for example in black boxes) are not handled as ordinary characters but in a special way.Depending on the library implementation the read operation may just stop, ignore those characters, convert them into different character sequences or tread them in their special way (like as end of text mark for example).You can check if a characters is a control character with iscntrl() for example.To remove these characters in every line you can use the following code:
#include <algorithm>
#include <cstdlib>
#include <cctype>
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
int main() {
string inPath("a.txt");
string outPath("b.txt");
string line;
ifstream in(inPath.c_str(), ifstream::in | ifstream::binary);
if ( ! in.is_open() ) {
cerr << "Error: Failed to read file \"" << inPath << "\"." << endl;
return EXIT_FAILURE;
}
ofstream out(outPath.c_str(), ofstream::out | ofstream::binary);
if ( ! out.is_open() ) {
cerr << "Error: Failed to write file \"" << outPath << "\"." << endl;
return EXIT_FAILURE;
}
while ( getline(in, line) ) {
/* this also removes line-feed and carrier-return */
line.erase(remove_if(line.begin(), line.end(), ::iscntrl), line.end());
out << line << '\n';
}
cout << "Done." << endl;
return EXIT_SUCCESS;
}

Answer 2

you can loop through each char in the file and use utility functions like isalpha(), isalnum() and isdigit() to make sure each char is is ascii, and skip out the others.
see http://www.cplusplus.com/reference/cctype/isalpha/

Answer 3

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string>
using std::string;
int die(string &msg) {
fprintf(stderr, "%s\n", msg.c_str());
exit(-1);
return -1; // Not really.
}
int
main(int argc, char **argv) {
string msg;
string inpt;
FILE *INPT;
string oupt;
FILE *OUPT;
int c;
(argc > 1) ||
(die(msg += "Missing filename arg."));
inpt += argv[1];
(oupt += inpt) += ".nxt";
(INPT = fopen(inpt.c_str(), "r")) ||
(die(((msg += "Can't open \"") += inpt) += "\" for input."));
(OUPT = fopen(oupt.c_str(), "w")) ||
(die(((msg += "Can't open \"") += oupt) += "\" for output."));
for (;(c = fgetc(INPT)) != EOF;) {
((unsigned)c < 0x80u) &&
(
(isprint(c)) ||
((iscntrl(c)) && (isspace(c)))
) &&
(fputc(c, OUPT));
}
fclose(OUPT);
fclose(INPT);
return 0;
}