What the point of using std::ios_base::binary?

by

The differences between binary and text modes are implementation
defined, but only concern the lowest level: they do not change the
meaning of things like << and >> (which insert and extract textual
data). Also, formally, outputting all but a few non-printable
characters (like '\n') is undefined behavior if the file is in text
mode.

For the most common OSs: under Unix, there is no distinction; both are
identical. Under Windows, '\n' internally will be mapped to the two
character sequence CR, LF (0x0D, 0x0A) externally, and 0x1A will be
interpreted as an end of file when reading. In more exotic (and mostly
extinct) OSs, however, they could be represented by entirely different
file types at the OS level, and it could be impossible to read a file in
text mode if it were written in binary mode, and vice versa. Or you
could see something different: extra white space at the end of line, or
no '\n' in binary mode.

With regards to always setting std::ios_base::binary: my policy for
portable files is to decide exactly how I want them formatted, set
binary, and output what I want. Which is often CR, LF, rather than just
LF, since that’s the network standard. On the other hand, most
Windows programs have no problems with just LF, but I’ve encountered
more than a few Unix programs which have problems with CR, LF; which
argues for systematically using just LF (which is easier, too). Doing
things this way means that I get the same results regardless of whether
I’m running under Unix or under Windows.

More Related Contents:

  1. Reading and writing a std::vector into a file correctly
  2. Why are C++ STL iostreams not “exception friendly”?
  3. How do I specify a pointer to an overloaded function?
  4. C++ std::set update is tedious: I can’t change an element in place
  5. How to overload std::swap()
  6. Alternative to vector
  7. How do I sort a vector of pairs based on the second element of the pair?
  8. Is there any real risk to deriving from the C++ STL containers?
  9. maximum value of int
  10. How to avoid memory leaks when using a vector of pointers to dynamically allocated objects in C++?
  11. how to provide a swap function for my class?
  12. How can I create my own comparator for a map?
  13. GCC STL bound checking
  14. comparing iterators from different containers
  15. How to reuse an ostringstream?
  16. Inspecting standard container (std::map) contents with gdb
  17. How are iterators and pointers related?
  18. Can I use CreateFile, but force the handle into a std::ofstream?
  19. Is there a production ready lock-free queue or hash implementation in C++ [closed]
  20. std::strings’s capacity(), reserve() & resize() functions
  21. all combinations of k elements out of n
  22. vs. vs. “iostream.h”
  23. What is the header?
  24. When does cout flush?
  25. C++ convert vector to vector
  26. Using std::map where V has no usable default constructor
  27. Comparing 3 modern c++ ways to convert integral values to strings
  28. Is it more efficient to copy a vector by reserving and copying, or by creating and swapping? [duplicate]
  29. Missing C++ header after updating OSX Command Line Tools 6.3
  30. Obtain container type from (its) iterator type in C++ (STL)

Leave a Comment