How does the code below work ? where is the counter for the for-loop and how can i reset the counter to line number 0.
for (std::string line;std::getline(ifs, line); )
{
}
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3 Answers
There is no need for a counter. This is equivalent to
std::string line;
while(getline(ifs, line))
{
}
There are methods to move the input iterator back to the beginning of the file. Something like: ifs.seekg(0, std::ios::beg); should do the trick.
Comments
Your for loop is equivalent to:
{
std::string line;
while (std::getline(ifs, line)) {
}
}
In other words: "keep iterating as long as getline returns true".
answered Oct 20, 2012 at 19:56
Branko Dimitrijevic
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4 Comments
Branko Dimitrijevic
@rajat Seek through the file.
rajat
I found a easier way , i just close and reopen the file . > ifs.close();ifs.open(filename);
dmckee --- ex-moderator kitten
@rajat ::shudder:: Use
seek. Just one system call instead of two, plus close/re-open introduces a race condition, and while errors related to that may be rare they will be effectively impossible to debug. For instance, on unix-like systems the file may have been deleted from the command line in the mean time and close and re-open will fail (because the file will be gone), while seeking will still work.And to reset the counter to line number 0 (i.e. to the beginning of stream) you should use
ifs.seekg (0, ios::beg);
