The Quantum Physicist The Quantum Physicist - 3 months ago 12
Linux Question

Pipe to my program as a log rotator

I'm trying to implement my own log rotator (create new log file whenever filesize reaches 10 MB). The part that reads the standard input and writes it to the file is this:

fstream file("log.txt", ios::out | ios::app);
while (std::cin >> lineInput) {
file << lineInput;
}


But the problem is that piped data gets ruined. Tabs and new lines are always lost. So for example if my program's name is
LogRotator
, then the command:

ls | ./LogRotator


Just concatenates all the file names together, like this:

LogRotatormain.oMakefile


while the output of
ls
is:

LogRotator main.o Makefile


My question: How can I make the standard streaming preserve everything, including tabs, newlines, etc.?

Answer

Thanks to Dieter L├╝cking's hint, I found the way to do it. So one has to use an unformatted read. The following works fine:

fstream file("log.txt", ios::out | ios::app);
while (getline(cin,lineInput,'\n'))
{
    file << lineInput;
}