Operating system(s) or programming environment(s)
Lubuntu 15.04 (vivid)
Qt Creator 3.1.1
- G++ 4.9.2
Libraries used:
Qt project file: ./CppStdFgetsExample2/CppStdFgetsExample2.pro
exists(../../ConsoleApplication.pri) { include(../../ConsoleApplication.pri) } !exists(../../ConsoleApplication.pri) { QT += core QT += gui greaterThan(QT_MAJOR_VERSION, 4): QT += widgets CONFIG += console CONFIG -= app_bundle TEMPLATE = app CONFIG(release, debug|release) { DEFINES += NDEBUG NTRACE_BILDERBIKKEL } QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra -Weffc++ unix { QMAKE_CXXFLAGS += -Werror } } SOURCES += main.cpp
#include <cassert> #include <fstream> #include <iostream> int main() { const std::string filename = "tmp.txt"; { std::ofstream file(filename.c_str()); const int zero = 0; file << zero << '\n' << 0 << '\n' << 1 << '\n' << 2 << '\n' << 3 << '\n' << 4 << '\n' << 5 << '\n' << 6 << '\n' << 7 << '\n' << 8 << '\n' << 9 << '\n' << 0 << '\n' << zero; } std::FILE* const file = std::fopen(filename.c_str(),"r"); const std::FILE * const file_before = file; const int buffer_size = 8; char buffer[buffer_size]; for (int i=0; ; ++i) { if (!std::fgets(buffer, buffer_size, file)) break; std::cout << i << ": <before>" << buffer << "<after>" << '\n'; assert(file_before == file && "Magic: the file is read sequential, yet file remains the same"); } } /* Screen output 0: <before>0 <after> 1: <before>0 <after> 2: <before>1 <after> 3: <before>2 <after> 4: <before>3 <after> 5: <before>4 <after> 6: <before>5 <after> 7: <before>6 <after> 8: <before>7 <after> 9: <before>8 <after> 10: <before>9 <after> 11: <before>0 <after> 12: <before>0<after> Press <RETURN> to close this window... */