Reading a LINE from a file

This is a discussion on Reading a LINE from a file within the C++ Programming forums, part of the General Programming Boards category; How can I make my program read a line from a file. I don't want it to stop on spaces, ...

  1. #1
    Reverse Engineer maxorator's Avatar
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    Reading a LINE from a file

    How can I make my program read a line from a file. I don't want it to stop on spaces, I want it to read the whole line.

  2. #2
    Registered User major_small's Avatar
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    use getline()

    for character arrays:std::cin.getline(char*,size,delim)
    for Strings:getline(std::cin,string,delim)

    examples:
    Code:
    char linech[20];
    std::string linestr;
    
    std::cin.getline(linech,20,'\n');
    getline(std::cin,linestr,'\n');
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  3. #3
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    Wow, I think this will be the first time I found something useful from MSDN that actually deals with standard code

    http://msdn.microsoft.com/library/de...estlsample.asp

    and here is the code sample, this uses the C++ standard String class by the way.

    Code:
    #include <string>
    #include <iostream>
    
    using namespace std ;
    
    int main()
    {
       string s1;
       cout << "Enter a sentence (use <space> as the delimiter): ";
       getline(cin,s1, ' ');
       cout << "You entered: " << s1 << endl;
    }

    basically, if you get rid of the third parameter (the ' ') then it will continue until it reaches a newline by default. such as the example below

    Code:
    #include <string>
    #include <iostream>
    
    using namespace std ;
    
    int main()
    {
       string s1;
       cout << "Enter a sentence: ";
       getline(cin,s1);
       cout << "You entered: " << s1 << endl;
    }
    EDIT: Darn, beaten to it.
    Last edited by Xipher; 10-30-2005 at 01:10 AM.
    If any part of my post is incorrect, please correct me.

    This post is not guarantied to be correct, and is not to be taken as a matter of fact, but of opinion or a guess, unless otherwise noted.

  4. #4
    Reverse Engineer maxorator's Avatar
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    Well I said "from a file", so...

  5. #5
    Reverse Engineer maxorator's Avatar
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    I thought this is problem is because I don't know how to use fgets, but:
    Code:
    while(fgets(run,100,pFile)){
    hello[ib]=run;
    ib=ib+1;
    }
    for(int i=0;i<7;i++){
    cout<<"begin\n"<<ib<<hello[i]<<"\nend"<<endl;
    }
    A part of my code. It doesn't read correctly, all pieces of hello are filled with the last line...

  6. #6
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    the getline example I used is usable with filestreams as well, just replace cin with the filestream

    EDIT
    Ok, I threw together a little demo of what I mean
    Code:
    #include <fstream>
    #include <iostream>
    #include <string>
    using namespace std;
    
    int main()
    {
            string InputBuffer;
            fstream InputFile;
            InputFile.open("testfile.txt", fstream::in);
            while(!InputFile.eof())
            {
                    getline(InputFile,InputBuffer);
                    cout << "Got one line: " << InputBuffer << endl;
            }
            InputFile.close();
            cout << endl << "All lines read and printed" << endl;
    }
    Yes, I know, the filename is hardcoded, but it worked to test with
    Last edited by Xipher; 10-30-2005 at 03:47 PM.
    If any part of my post is incorrect, please correct me.

    This post is not guarantied to be correct, and is not to be taken as a matter of fact, but of opinion or a guess, unless otherwise noted.

  7. #7
    & the hat of GPL slaying Thantos's Avatar
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    Quote Originally Posted by maxorator
    Well I said "from a file", so...
    string version of getline:
    getline takes a reference to an istream as its first parameter. It can be anything that can be reduced to an istream. ifstreams, iostreams, istringstream, etc all derive from istream which means they can all be used as the first parameter. Also on many systems your input and output are files.

    io version of getline:
    anything that inherits from istream also inherits the member function getline. So see above

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