I need to read a file, which is an .asc document using QT Framework.
I need to check the file for specific Strings, for example "(Name)".
The Numbers after the specific String have to be saved in another .txt file.
So I tried to use a for loop connected with a getline() statement, whilst an if statement should be checking if the predefined String was found already.
If the String was found I am using a string variable .assign() method to input the whole matching line to another string.
But sadly it is still not working, maybe there is a logical failure, so I am asking for your help!
std::string line;
std::string search = "(Name)";
std::string content;
std::ifstream ifs("C:/PROG/EMS/LD1/analyse_led");
for(unsigned int curLine = 0; std::getline(ifs, line); curLine++) {
if (line.find(search) != std::string::npos) {
content.assign( (std::istreambuf_iterator<char>(line) ),
(std::istreambuf_iterator<char>() ) );
}
}
Of course I implemented all related include files above, thanks for your help!
If you need more information let me know in the comments.
content and line are both std::strings, just do
content = line;
or
content = std::move(line);
if you don't need to do anything else with line afterwards. (line will be empty after this).
I'm not sure what you are trying to achieve with istreambuf_iterator, but I'm sure it isn't going to work...
Related
I am trying to read about 2 lines from a file of text into a std::string in c plus plus. I have looked through several answers and found none that work on my device. Can anyone tell me what I am doing wrong? The method is currently returning a null string, and doesn't correctly open the file or read it at all.
std::string readFile(std::string filename) {
std::ifstream infile;
infile.open(filename);
std::string output;
if (infile.is_open()) {
while(infile.good()) {
infile >> output;
}
}
infile.close();
return output;
}
Not sure what file you are trying to open but that's a completely separate problem. The code you've written will open a file if you give it a path to a file that it can open. Check your current working directory and confirm the path is correct.
Even after you solve that problem, you're going to have more problems though.
I expect that you are confused because you are repeatedly overwriting output with this line:
infile >> output;
perhaps you meant to declare output as a std::stringstream
And for me it doesn't return an empty string, it returns the last word of the file. I guess it depends what's in your file.
I'm trying to create a student database system for a school project. I'm trying to create a function that will search a .txt file for the student id and return all of the other variables on the string. This is working great if I search for the id of the student on the first line of the txt file but isn't capturing anything if I search for a student on another line. Am I missing something obvious?
The student data is 16 strings delimited by commas on each line. The student ID is the first string.
Thanks for any assistance!
StudentType findStudent(int studentToFind)
{
ifstream inFile;
inFile.open("students.txt");
string currentLine;
string dataRead[16];
istringstream is;
int currentStudent;
if (inFile)
{
while (getline(inFile, currentLine))
{
is.str(currentLine);
for (int i = 0; i < 16; i++)
{
getline(is, dataRead[i], ',');
}
currentStudent = stoi(dataRead[0]);
if (currentStudent == studentToFind)
{
/*
Do stuff here
*/
inFile.close();
return foundStudent;
}
cin.ignore(); // Not sure if this is needed but I was trying to
// clear the \n char if that was causing the issue
}
}
}
First : you aren't using cin, so get rid of cin.ignore().
Second : you should make sure you ALWAYS close infile at the end... so I would suggest not returning early or closing early, but using a break statement to exit your loop and then have a single return of whether you found it or not.
Third: Now that you removed all the 'gorp' we can finally hone in on the problem ... effectively the question is do we read all the lines?
Well let's check that, try printing out currentLine each time at the beginning of the while loop, if you know currentLine is updated properly, is is getting updated each time? yes...
ok then look at your next loop let's print out currentStudent each time... does currentStudent print the right value for each line? i.e. is the getline write into dataRead[i] actually writing what you think it should be to the right space?
Did you find the problem yet?
This is the kind of problem you need to learn how to solve yourself using print statements and a debugger. That what its for. If you are in visual studio run in debug mode and step through it... if not, use gdb. learn it and get used to it, you'll be using it a lot!
good luck
Is it possible to edit text in a file using cpp code. Already there is related question on it, but it doesn't solve my problem. Kindly help me out.
I have given a rough code line on this.
seek() through the file and try to replace the contents with new string from that point till the end of line.
I need the "hello" string be placed and must be the end of line.
like if we have new.txt as
ABCDEFGHIJKLMNOPQRST
If I want the file content to be changed as
ABCDEHELLO
I am getting the file content as
ABCDHELLOJKLMNOPQRST
fstream file("new.txt",fstream::in|fstream::out);
file.open();
while(getline(file,str))
{
if(value==strstr())
{
file.seekp(pos);
str.erase(pos,len);//len specifies the value till end of str
str.replace(pos,6,"hello");
char *d=new char[str.length()+1];
strcpy(d,str.c_str());
file.write(d,strlen(d));
delete [] d;
}
}
If I could copy the file contents to the string, manipulate it, then copy to the new file then it is possible.
Is it possible to change the contents in the same file. If so kindly help me out, I am struck in this. If the replacing string is longer than the one actually existing then this works, but if the replacing string is smaller than the one which is actually existing then I am unable to do.
if you case is only one line in the file you can easily separate the I/O process in two stages. Read the file and get the position of the text. then close the file and reopened as out then write the string you want. Note that this will work if you have one line in the file
check the following code
std::string value = "GFGHHFGHH";
std::string str;
std::fstream file("new.txt", std::ios::in);
std::size_t found;
while (file >> str)
{
found = str.find(value);
if (found != std::string::npos)
{
str.erase(value.length() );
str.replace(found, 6, "hello");
}
}
file.close();
file.open("new.txt", std::ios::out);
file << str;
file.close();
You can do it using system call for sed:
string s="sed -i s/hey/ho/g file0102.txt";
system(s.c_str());
I can read the number of lines easy, using:
ifstream in(file);
string content;
while(getline(in, content))
{
// do stuff
}
Or I can read the number of words and characters easy using something like:
ifstream in(file)
string content;
int numOfCharacters = 0;
int numOfWords = 0;
while(in >> content)
{
++numOfWords;
numOfCharacters += content.size();
}
But I dont want to read the file twice. How can I read the file once, and find out the number of lines, words and characters?
PS: I would welcome a Boost sugestion, if there is a easy way.
Thank you.
Read the line and for each line count the words. See stringstream for the second part.
(I'm not giving more information, that looks too much like an homework).
This could be done with a trivial boost.spirit.qi parser.
Sticking with the iostreams solution: you could create a strstream out of each line read via getline(), and do the word/char counting operations on it, accumulating across all the lines.
can i please get some guidance to constructing a parser for an input file, I've been looking for a help for weeks, the assignment is already past due, I would just like to know how to do it.
The commented code is what I've tried, but i have a feeling it is more serious than that. I have a text file and I want to parse it to count the number of times that words appear in the document.
Parser::Parser(string filename) {
//ifstream.open(filename);
// source (filename, fstream::in | fstream::out);
}
The commented code is what I've tried, but i have a feeling it is more serious than that.
I have a feeling you haven't tried a thing. So I am going to do the same.
Google is your friend.
To read a word:
std::ifstream file("FileName");
std::string word;
file >> word; // reads one word from a file.
// Testing a word:
if (word == "Floccinaucinihilipilification")
{
++count;
}
// Count multiple words
std::map<std::string, int> count;
// read a word
++count[word];
// To read many words from a file:
std::string word;
while(file >> word)
{
// You have now read a word from a file
}
Note: That is a real word :-)
http://dictionary.reference.com/browse/floccinaucinihilipilification
Take a look at the answers in How do you read a word in from a file in C++? . The easiest way is to use an ifstream and operator>> to read single words. You can then use a standard container like vector (as mentioned in the link above) or map<string, int> to remember the actual count.