CODEWITHSUNDEEP
c++fileio
SantasNotReal
SantasNotReal

Reputation: 1281

Reading a specif line from a txt file in c++

So, I've found the specific line of a file that I want to read, but what I've got isn't working:

    string str;
int target = 0;
ifstream record;

record.open("Record.txt");
target = std::count(std::istreambuf_iterator<char>(record), std::istreambuf_iterator<char>(), '\n') - 8;
cout << target << endl;

for(int lineNum = 0; lineNum <= target; lineNum++)
{
    getline(record, str);
    if(lineNum == target)
    {
        cout <<"the id: "<< str << endl;
    }
}

In the above, I use std::count to count the lines of a file. I know that I'll always want to read the eigth line from the bottom, so I set my target to that. Next, I loop through each line up to target times, and do a check to see if i'm at the target line. If so, then cout the line.

However, it's not giving me anything. For a file with 22 lines, I get the following output:

14
the id:

Can someone point out what I'm doing wrong or give me some hints? Thanks!

Upvotes: 0

Views: 179

Answers (1)

hmjd
hmjd

Reputation: 122001

The record stream will be eof() after the std::count() call but the code never checks the return value of std::getline() so is unaware that it is failing: always check return value of read operations. This means that str is never populated hence nothing is printed after the "thid id: " message.

You need to reset the stream or re-open it.

Upvotes: 3

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