![]() ![]() If this parameter is omitted the file is opened as a text file. If the file already exists, the open() fails. If the file does not already exist, the open() fails. ![]() This mode is implied when ios::out is specified (including implicit specification for ofstream) and neither ios::ate nor ios::app is specified. If the file already exists, its contents are truncated (discarded). For fstream it says that output operations are to be allowed. ios::out is implied by construction and opens of ofstreams. If the file does not already exist, the open() fails. It is legal to include ios::in in the modes of an ostream, in which case it implies that the original file (if it exists) should not be truncated. For fstreams it indicates that input operations should be allowed if possible. ios::in is implied by construction and opens of ifstreams. ios::app implies ios::out.Ī seek to the end of the file is performed during the open(). Subsequent data written to the file is always appended to the end of file. (Because the or’ingreturns an int, open() takes an int rather than an open_mode argument.) The meanings of these bits in mode are:Ī seek to the end of file is performed. The members of open_mode are bits that may be or’ed together. "(INCORE)" for a temporary binary file that is only set up in virtual memoryįor more detailed information, please refer to the "C Library Functions" manual."(SYSDTA)", "(SYSOUT)", "(SYSLST)" for the appropriate system file."link= linkname", where linkname is a BS2000 link name.ios::failbit is set in f’s error status on failure. Failure occurs if f is already open, or the C runtime system call open() fails. ![]() If the file does not already exist, an attempt is made to create it unless ios::nocreate or ios::in is set. Void f.open(char * name, int mode, int prot) f’serror state is cleared except on failure, which is when the C runtime system detects afailure in the system call close(). A failure sets ios::failbit in f’s error state.Ĭloses any associated filebuf and thereby breaks the connection of the f to a file. A failure occurs when f is already connected to afile. Member functionsĬonnects f to the file descriptor fd. If ptr is NULL or len is 0, the filebuf is unbuffered. The error state (io_state) of the constructed xstream indicates failure in case the open fails.Ĭonstructs an xstream connected to file descriptor fd, which must be already open.Ĭonstructs an xstream connected to file descriptor fd, and, in addition, initializes theĪssociated filebuf to use the len bytes at ptr as the reserve area. For a description of parameters name and mode, see under open() below.
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