Re: help old VBasic programmer with simple file read , Please :)

From:
 James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 14 Jun 2007 01:02:54 -0700
Message-ID:
<1181808174.989308.39960@o11g2000prd.googlegroups.com>
On Jun 14, 6:30 am, Rolf Magnus <ramag...@t-online.de> wrote:

 marks542...@yahoo.com wrote:

I have a program in Basic that reads a file , looks for lines
containing a specific string , and lists them.

I am trying to do the same thing in C in a search for speed
with very large files.


If speed is a criteria, you may have to write your own. None of
the standard library functions will do a BM search, for example.

I have a program working until I try testing for the substring.
heres the code I have:


    [...]

char str[] = "Geom";

int main(int argc, char* argv[])
{
  string line;
  char *pdest;
  ifstream myfile ("C:\\Documents and Settings\\Owner\\My Documents\
\downloads\\stimuli\\stimV4wall2.pz2");
  if (myfile.is_open())
  {
    while (! myfile.eof() )


This loop is incorrect. See question 15.5 in the "C++ FAQ lite".

    {
      getline (myfile,line);
pdest = strstr( line, str );


Why aren't you using std::string::find?


Or std::search. I'd declare the search string as an std::string
as well, and merge this and the following line into something
like:

    if ( std::search( line.begin(), line.end(), str.begin(),
str.end() )
            != line.end() ) {
        // ...
    }

Somehow, it seems more idiomatic.

--
James Kanze (GABI Software, from CAI) email:james.kanze@gmail.com
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