Friday, April 1, 2011

getline() -- how many kinds in C/C++ std library

(Note All the getline() functions below are designed to return text from a File or cin -- actually a one-way stream. Inapplicable to sockets.)

1) Most documentations mention the c-str-based istream::getline() http://www.cplusplus.com/reference/istream/istream/getline/. However,
2) http://www.cplusplus.com/reference/string/getline/ is another getline(). Unlike the c-str versions of istream::getline(), this std::string version is implemented as free function instead of member function.


Between these 2 getline() functions,
- One uses c-str; the other uses c++ string class.
- One is a member function; the other a free function

Similarities --
- both use streams, therefore unusable in C.

http://www.learncpp.com/cpp-tutorial/132-input-with-istream/ discusses both.

There's an IKM question on the member function (1).

3) http://www.gnu.org/software/libc/manual/html_node/Line-Input.html describes a prehistoric ANSI-C standard library function -- not using string Class or istream Class. http://crasseux.com/books/ctutorial/getline.html is a short and sharp tutorial on it.

------- philosophically -------
We can't assume the most "everyday" programming tasks in a major language are always well-covered online -- completely covered, with the confusing details pointed out. Reading a text file is basic but supported by a confusing bunch of alternatives, all named getline().

http://www.augustcouncil.com/~tgibson/tutorial/iotips.html does describe pitfalls of istream::getline()

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