C-style file input/output
The C I/O subset of the C++ standard library implements C-style stream input/output operations. The <cstdio> header provides generic file operation support and supplies functions with narrow and multibyte character input/output capabilities, and the <cwchar> header provides functions with wide character input/output capabilities.
C streams are objects of type std::FILE that can only be accessed and manipulated through pointers of type std::FILE* (Note: while it may be possible to create a local object of type std::FILE by dereferencing and copying a valid FILE*, using the address of such copy in the I/O functions is undefined behavior). Each C stream is associated with an external physical device (file, standard input stream, printer, serial port, etc).
C streams can be used for both unformatted and formatted input and output. They are locale-sensitive and may perform wide/multibyte conversions as necessary. Unlike C++ streams, where each stream is associated with its own locale, all C streams access the same locale object: the one most recently installed with std::setlocale.
Besides the system-specific information necessary to access the device (e.g. a POSIX file descriptor), each C stream object holds the following:
Contents |
Functions
Types
| Defined in header
<cstdio> | |
| Type | Definition |
| FILE | type, capable of holding all information needed to control a C I/O stream |
| fpos_t | type, capable of uniquely specifying a position in a file |
Macros
| Defined in header
<cstdio> | |
| stdin stdout stderr |
expression of type FILE* associated with the input stream expression of type FILE* associated with the output stream expression of type FILE* associated with the error output stream (macro constant) |
| EOF |
integer constant expression of type int and negative value (macro constant) |
| FOPEN_MAX |
number of files that can be open simultaneously (macro constant) |
| FILENAME_MAX |
size needed for an array of char to hold the longest supported file name (macro constant) |
| BUFSIZ |
size of the buffer used by std::setbuf (macro constant) |
| _IOFBF _IOLBF _IONBF |
argument to std::setbuf indicating fully buffered I/O argument to std::setbuf indicating line buffered I/O argument to std::setbuf indicating unbuffered I/O (macro constant) |
| SEEK_SET SEEK_CUR SEEK_END |
argument to std::fseek indicating seeking from beginning of the file argument to std::fseek indicating seeking from the current file position argument to std::fseek indicating seeking from end of the file (macro constant) |
| TMP_MAX |
maximum number of unique filenames that can be generated by std::tmpnam (macro constant) |
| L_tmpnam |
size needed for an array of char to hold the result of std::tmpnam (macro constant) |
