Oct 30, 2011 · tellp gives the current position of the put pointer. outfile.seekp (pos-7) statement moves the put pointer 7 bytes backwards from the its current position. In your example, it was pointing beyond the string "This is an apple" If you do pos-7, it goes to the location where 'n' letter is present. It overwrites the string " sam" from there.

Apr 24, 2014 · Why do tellg() and tellp() always come together? And how can we separate them from each other?

My assumption was that the difference between tellp() at two points in my output sequence would correspond to the number of intervening bytes. Unfortunately, at least in my Gnu C++ environment, cout does not maintain the fiction of a stream position. Every cout.tellp() call returns …

Jan 25, 2013 · I was just wondering why the member functions tellg() defined in basic_istream<> class and tellp() defined in basic_ostream<> class have different names. Is that because basic_fstream<> is derived from basic_istream<> and basic_ostream<> ?

Apr 5, 2020 · The standard actually doesn't guarantee any specific value for tellg, only that if seekg is run sometime afterwards on its output, it will put the stream into the same place that it was. In any case, the output of tellg is implementation-defined. It doesn't even have to be convertible to an integral type. In terms of implementations, generally files opened in binary mode (and in text mode for ...

May 29, 2013 · Say I wanted to get the difference (in int) between two tellp() outputs. The tellp() output could be huge if a big file is written so it is not safe to say store it inside a long long. Is there a ...

Jun 6, 2016 · The easiest but not faster method is: auto nLength = strm.str().length(); Regarding s_double position - it is easy to answer your question by examining the content of this stream in a debugger or print it. You will see that double could be "0.554213" for 0.554212545 or "1" for 1 so string length for defferent doubles is complitely different.

Jan 19, 2018 · From cppreference, this is expected behaviour: app: seek to the end of stream before each write [...] ate: seek to the end of stream immediately after open You want to open the file with ate if you want the file to be seeked before you write anything.

Jan 17, 2019 · I have a class that has a filestream of type ofstream. The constructor opens the file in append mode and all the messages always get written at the end of the file. I need to write into outputFile...

Jan 23, 2018 · I was looking at seekp and tellp() functionality. In below code, tellp() returns -1 after f2.seekp(10). I could not understand why -1 is returned. This I tested in both compilers (Visual Studio as ...