C-style file input/output - cppreference.com
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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 denoted by objects of type std::FILE that can only be accessed and manipulated through pointers of type std::FILE*. Each C stream is associated with an external physical device (file, standard input stream, printer, serial port, etc).
Types
| object type, capable of holding all information needed to control a C I/O stream (typedef) [edit] | |
| complete non-array object type, capable of uniquely specifying a position in a file, including its multibyte parse state (typedef) [edit] | |
Predefined standard streams
expression of type FILE* associated with the input streamexpression of type FILE* associated with the output streamexpression of type FILE* associated with the error output stream (macro constant) [edit] | |
Functions
Defined in header | |
File access | |
| opens a file (function) [edit] | |
| open an existing stream with a different name (function) [edit] | |
| closes a file (function) [edit] | |
| synchronizes an output stream with the actual file (function) [edit] | |
| switches a file stream between wide character I/O and narrow character I/O (function) [edit] | |
| sets the buffer for a file stream (function) [edit] | |
| sets the buffer and its size for a file stream (function) [edit] | |
Direct input/output | |
| reads from a file (function) [edit] | |
| writes to a file (function) [edit] | |
Unformatted input/output | |
Byte/multibyte character | |
| gets a character from a file stream (function) [edit] | |
| gets a character string from a file stream (function) [edit] | |
| writes a character to a file stream (function) [edit] | |
| writes a character string to a file stream (function) [edit] | |
| reads a character from stdin (function) [edit] | |
(deprecated in C++11)(removed in C++14) |
reads a character string from stdin (function) [edit] |
| writes a character to stdout (function) [edit] | |
| writes a character string to stdout (function) [edit] | |
| puts a character back into a file stream (function) [edit] | |
Wide character | |
| gets a wide character from a file stream (function) [edit] | |
| gets a wide string from a file stream (function) [edit] | |
| writes a wide character to a file stream (function) [edit] | |
| writes a wide string to a file stream (function) [edit] | |
| reads a wide character from stdin (function) [edit] | |
| writes a wide character to stdout (function) [edit] | |
| puts a wide character back into a file stream (function) [edit] | |
Formatted input/output | |
Byte/multibyte character | |
| reads formatted input from stdin, a file stream or a buffer (function) [edit] | |
(C++11)(C++11)(C++11) |
reads formatted input from stdin, a file stream or a buffer using variable argument list (function) [edit] |
(C++11) |
prints formatted output to stdout, a file stream or a buffer (function) [edit] |
| prints formatted output to stdout, a file stream or a buffer using variable argument list (function) [edit] | |
Wide character | |
| reads formatted wide character input from stdin, a file stream or a buffer (function) [edit] | |
(C++11)(C++11)(C++11) |
reads formatted wide character input from stdin, a file stream or a buffer using variable argument list (function) [edit] |
| prints formatted wide character output to stdout, a file stream or a buffer (function) [edit] | |
| prints formatted wide character output to stdout, a file stream or a buffer using variable argument list (function) [edit] | |
File positioning | |
| returns the current file position indicator (function) [edit] | |
| gets the file position indicator (function) [edit] | |
| moves the file position indicator to a specific location in a file (function) [edit] | |
| moves the file position indicator to a specific location in a file (function) [edit] | |
| moves the file position indicator to the beginning in a file (function) [edit] | |
Error handling | |
| clears errors (function) [edit] | |
| checks for the end-of-file (function) [edit] | |
| checks for a file error (function) [edit] | |
| displays a character string corresponding of the current error to stderr (function) [edit] | |
Operations on files | |
| erases a file (function) [edit] | |
| renames a file (function) [edit] | |
| creates and opens a temporary, auto-removing file (function) [edit] | |
| returns a unique filename (function) [edit] | |
Macro constants
integer constant expression of type int and negative value (macro constant) | |
| maximum number of files that can be open simultaneously (macro constant) | |
size needed for an array of char to hold the longest supported file name (macro constant) | |
_PRINTF_NAN_LEN_MAX (C++26) |
the maximum number of characters output for any (possibly negated) NaN value (macro constant) |
| size of the buffer used by std::setbuf (macro constant) | |
| indicates the buffering mode (fully buffered / line buffered / unbuffered) to be set by std::setvbuf (macro constant) | |
| indicates the offset origin (beginning / current position / end) to be used by std::fseek (macro constant) | |
| maximum number of unique filenames that can be generated by std::tmpnam (macro constant) | |
size needed for an array of char to hold the result of std::tmpnam (macro constant) |