The GNU C++ Iostream Library - Istream Housekeeping

Miscellaneous istream utilities

Use these methods for housekeeping on istream objects:

Method int istream::gcount ()

Report how many characters were read from this istream in the last unformatted input operation.

Method int istream::ipfx (int keepwhite)

Ensure that the istream object is ready for reading; check for errors and end of file and flush any tied stream. ipfx skips whitespace if you specify 0 as the keepwhite argument, and ios::skipws is set for this stream.

To avoid skipping whitespace (regardless of the skipws setting on the stream), use 1 as the argument.

Call istream::ipfx to simplify writing your own methods for reading istream objects.

Method void istream::isfx ()

A placeholder for compliance with the draft ansi standard; this method does nothing whatever.

If you wish to write portable standard-conforming code on istream objects, call isfx after any operation that reads from an istream ; if istream::ipfx has any special effects that must be cancelled when done, istream::isfx will cancel them.

Method istream& istream::ignore ([int n] [, int delim])

Discard some number of characters pending input. The first optional argument n specifies how many characters to skip. The second optional argument delim specifies a ``boundary'' character: ignore returns immediately if this character appears in the input.

By default, delim is EOF ; that is, if you do not specify a second argument, only the count n restricts how much to ignore (while input is still available).

If you do not specify how many characters to ignore, ignore returns after discarding only one character.

Method istream& istream::putback (char ch)

Attempts to back up one character, replacing the character backed-up over by ch. Returns EOF if this is not allowed. Putting back the most recently read character is always allowed. (This method corresponds to the C function ungetc .)

Method istream& istream::unget ()

Attempt to back up one character.