C++ In a Nutshell

Name

ios_base::openmode type — Open mode bits

Synopsis

typedef  . . .  openmode
typedef  . . .  open_mode
static const openmode app
static const openmode ate
static const openmode binary
static const openmode in
static const openmode out
static const openmode trunc
               

The ios_base::openmode type is an integer, enum, or bitset type (the exact type is implementation-defined) that defines the mode for opening a file. The open_mode type is an integral type that represents the same information. Some functions that take an openmode parameter have an overloaded version that accepts an open_mode parameter and has the same functionality as its openmode counterpart. The open_mode type and related functions are deprecated, so you should use the openmode versions.

Table 13-16 lists the openmode literals and their meanings. (Refer to the <fstream> section of this chapter for the most common use of ios_base::openmode and the permitted combinations of openmode literals.) The openmode type is also used for the basic_streambuf::pubseekoff and pubseekpos functions, and for related functions.

Table 13-16. openmode literals

Literal	Description
app	Seeks to end-of-file before each write
ate	Seeks to end-of-file immediately after opening
binary	Reads and writes in binary mode (default is text)
in	Opens for input (reading)
out	Opens for output (writing)
trunc	Truncates file to zero length

See Also

<bitset>, basic_filebuf ...