C++ In a Nutshell

Name

fopen function — Opens a file

Synopsis

FILE* fopen(const char* filename, const char* mode)

The fopen function opens a file.

The filename parameter specifies the filename in an implementation-defined manner. The mode parameter specifies how to open the file. The mode must begin with one of the strings listed in Table 13-4. Additional characters can follow, and the interpretation of the extra characters is implementation-defined. Mode strings are case-sensitive.

Table 13-4. File open modes

Mode string	Description
a	Append: opens an existing file for appending, that is, every write is forced to the end of the file. If the file to be opened does not exist, a creates it.
r	Read: opens an existing file for reading.
w	Write: creates a new file for writing. If the file already exists, w truncates it to zero length.
ab	Append in binary mode.
rb	Read in binary mode.
wb	Write in binary mode.
a+	Append update: opens a file in append mode and allows it to be read.
r+	Read update: opens an existing file for reading, and also allows writing.
w+	Write update: creates a new file for writing, and also allows reading. If the file already exists, w+ truncates it to zero length.
ab+ or a+b	Append update in binary mode.
rb+ or r+b	Read update in binary mode.
wb+ or w+b	Write update in binary mode.

See Also

fclose function, freopen function