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Problem with reading files from text source.

Posted on 2004-11-24
Medium Priority
Last Modified: 2010-04-17
Hello Experts,

When I use this function...

     ifstream inFile("filename");  // where file name is a literal string.

my code compile without error.

but when I use this code...

     string myFileName = "filename";   // where filename is a litteral string and myFileName contains the value "filename"
     ifstream inFile(myFileName);      

I get this compilation error...

     cannot convert parameter 1 from 'std::string' to 'const char *'

How can I fix this?  And what am I doing wrong?

thank you,


Question by:travishaberman
  • 4
LVL 11

Assisted Solution

lbertacco earned 1000 total points
ID: 12672132
You need to pass the filename as an ASCII_Z (aka C style) string.

Just use:

 string myFileName = "filename";   // where filename is a litteral string and myFileName contains the value "filename"
     ifstream inFile(myFileName.c_str());      

Accepted Solution

Tex54 earned 1000 total points
ID: 12672142
its seems the infile method is trying to take a char array, rather then just a string literal.

instead of this line:

string myFileName = "filename";

do this:

char myFileName[] = "filename"

so your code becomes:

     char myFileName[] = "filename"
     ifstream inFile(myFileName);

Regards Thomas    


Author Comment

ID: 12672180
I allready tried that, and it works... but then my getline function is no good.  That is, I have to use this...

   inFile.getline(char, int)  <-- in this case I have to know the size of my     char array[size]     in order to acomidate the entire line.

instead of this

     getline(ifstream, string)     <-- in this I dont have to know the size because the string grows dynamically.

if I use the function you suggest the second getline function will give me a similar compilation error.

Any thoughts?

Thank you,

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Author Comment

ID: 12672186
My last post was addressed to lbertacco let me examine your suggestion Tex54..  Be right back.


Author Comment

ID: 12672253
I am still getting problems.. Let me approac this from a different angle.  I need to prompt a user for a file name.  Then I need to open the file and read in one line of it at a time.  I would like to use this getline funciton because then, no matter the line lenght, it will read the entire line and store it to a string. So,

What is the best way to approach that?

Thank you,


Author Comment

ID: 12672322
You know what.. I figured it all out! But, both of your suggestions were fine for my original quesiton.  So thank you.


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