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How do you read a line from a file to a string?

Posted on 1997-06-25
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Last Modified: 2011-04-14
I'm trying to read a file with a loop and put each line in a cstring. Here's my code:

string messageBuffer;
while(!messageFile.eof())
 { messageBuffer = "";
   getline(messageFile, messageBuffer);
   if(messageBuffer == "")
    { messageBuffer = "\n"; }
   sendToServer(s, messageBuffer, NO);
 }
This works fine for most lines, and doesn't save the \n to the cstring, just like it's supposed to, but when it gets to a blank line, where the \n is the only thing on the line, it totally skips it and goes on to the next line. If my file's like this:

Test 1

Test 2

-and I read it with this loop, it ends up being like:

Test 1
Test 2

-I tried using the cstring function:
messageBuffer.read_line(messageFile);
instead of:
getline(messageFile, messageBuffer);

-it gives the exact same results, which makes me think that the cstring class won't let it return just nothing, which what it should do if a \n is stripped off a line w/ just \n.

I tried this exact same loop using char messageBuffer[100] and char functions instead, and it works perfectly.

Also, tabs seem to be stripped out when they're saved to a string as well. Does anyone know what's wrong? Thanks.
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Question by:DarkNova
3 Comments
 

Author Comment

by:DarkNova
ID: 1164128
Edited text of question
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Expert Comment

by:strobert
ID: 1164129
I don't have the source code to read_line handy at the moment, but it looks like it is behaving like a stream >> operator to a string which eats whitespace.

use fscanf or a combo of fgets and sscanf to do formatted input reading.
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Accepted Solution

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mann061997 earned 50 total points
ID: 1164130
getline is defined as:

template<class E, class Ti, class T, class A>
    basic_istream<E, Ti>& getline(
        basic_istream <E, Ti>& is,
        basic_string<E, T, A>& str,
        E delim = Ti::newline());

Since you only supplied the first 2 parameters the delimiter
is set to the default value newline. The delimiter is not
appended to the string when it is encountered.

So you could either
- test for messageBuffer.IsEmpty() && !messageFile.eof() and
  generate a \n in these cases
- use char functions as you already mentioned
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