Standard library header <cstdio>

 

C++

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Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Standard library headers

Language support <cfloat> <climits> <compare> (C++20) <contracts> (C++26) <coroutine> (C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint> (C++11) <cstdlib> <exception> <initializer_list> (C++11)    <limits> <new> <source_location> (C++20) <stdfloat> (C++23) <typeinfo> <version> (C++20) Concepts <concepts> (C++20) Diagnostics <cassert> <cerrno> <debugging> (C++26) <stacktrace> (C++23) <stdexcept> <system_error> (C++11) Memory management <memory> <memory_resource> (C++17) <scoped_allocator> (C++11) Metaprogramming <meta> (C++26) <ratio> (C++11) <type_traits> (C++11)

General utilities <any> (C++17) <bitset> <bit> (C++20) <charconv> (C++17) <expected> (C++23) <format> (C++20) <functional> <optional> (C++17) <stdbit.h> (C++26) <tuple> (C++11) <typeindex> (C++11) <utility> <variant> (C++17) Containers <array> (C++11) <deque> <flat_map> (C++23) <flat_set> (C++23) <forward_list> (C++11) <hive> (C++26) <inplace_vector> (C++26)    <list> <map> <mdspan> (C++23) <queue> <set> <span> (C++20) <stack> <unordered_map> (C++11) <unordered_set> (C++11) <vector> Iterators <iterator> Ranges <generator> (C++23) <ranges> (C++20)

Algorithms <algorithm> <numeric> Strings <cctype> <cstring> <cuchar> (C++11) <cwchar> <cwctype> <string_view> (C++17) <string> Text processing <clocale> <codecvt> (C++11/17/26*) <locale> <regex> (C++11) <text_encoding> (C++26)    Numerics <cfenv> (C++11) <cmath> <complex> <linalg> (C++26) <numbers> (C++20) <random> (C++11) <simd> (C++26) <stdckdint.h> (C++26) <valarray> Time <chrono> (C++11) <ctime> C compatibility <ccomplex> (C++11/17/20*) <ciso646> (until C++20) <cstdalign> (C++11/17/20*) <cstdbool> (C++11/17/20*) <ctgmath> (C++11/17/20*)

Input/output <cinttypes> (C++11) <cstdio> <filesystem> (C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print> (C++23) <spanstream> (C++23) <sstream> <streambuf> <strstream> (C++98/26*) <syncstream> (C++20) Concurrency support <atomic> (C++11) <barrier> (C++20) <condition_variable> (C++11) <future> (C++11) <hazard_pointer> (C++26) <latch> (C++20) <mutex> (C++11) <rcu> (C++26) <semaphore> (C++20) <shared_mutex> (C++14) <stdatomic.h> (C++23) <stop_token> (C++20) <thread> (C++11) Execution support <execution> (C++17)

 

This header was originally in the C standard library as <stdio.h>.

This header is part of the C-style input/output library.

Types
FILE	object type, capable of holding all information needed to control a C I/O stream (typedef)
fpos_t	complete non-array object type, capable of uniquely specifying a position in a file, including its multibyte parse state (typedef)
size_t	unsigned integer type returned by the sizeof operator (typedef)
Macros
NULL	implementation-defined null pointer constant (macro constant)
stdinstdoutstderr	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_SETSEEK_CURSEEK_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)
Functions
File access
fopen	opens a file (function)
freopen	open an existing stream with a different name (function)
fclose	closes a file (function)
fflush	synchronizes an output stream with the actual file (function)
setbuf	sets the buffer for a file stream (function)
setvbuf	sets the buffer and its size for a file stream (function)
Direct input/output
fread	reads from a file (function)
fwrite	writes to a file (function)
Unformatted input/output
Narrow character
fgetcgetc	gets a character from a file stream (function)
fgets	gets a character string from a file stream (function)
fputcputc	writes a character to a file stream (function)
fputs	writes a character string to a file stream (function)
getchar	reads a character from stdin (function)
gets (deprecated in C++11)(removed in C++14)	reads a character string from stdin (function)
putchar	writes a character to stdout (function)
puts	writes a character string to stdout (function)
ungetc	puts a character back into a file stream (function)
Formatted input/output
Narrow/multibyte character
scanffscanfsscanf	reads formatted input from stdin, a file stream or a buffer (function)
vscanfvfscanfvsscanf (C++11)(C++11)(C++11)	reads formatted input from stdin, a file stream or a buffer using variable argument list (function)
printffprintfsprintfsnprintf (C++11)	prints formatted output to stdout, a file stream or a buffer (function)
vprintfvfprintfvsprintfvsnprintf (C++11)	prints formatted output to stdout, a file stream or a buffer using variable argument list (function)
File positioning
ftell	returns the current file position indicator (function)
fgetpos	gets the file position indicator (function)
fseek	moves the file position indicator to a specific location in a file (function)
fsetpos	moves the file position indicator to a specific location in a file (function)
rewind	moves the file position indicator to the beginning in a file (function)
Error handling
clearerr	clears errors (function)
feof	checks for the end-of-file (function)
ferror	checks for a file error (function)
perror	displays a character string corresponding of the current error to stderr (function)
Operations on files
remove	erases a file (function)
rename	renames a file (function)
tmpfile	creates and opens a temporary, auto-removing file (function)
tmpnam	returns a unique filename (function)

Synopsis

namespace std {
  using size_t = /* see description */;
  using FILE = /* see description */;
  using fpos_t = /* see description */;
}

#define NULL /* see description */
#define _IOFBF /* see description */
#define _IOLBF /* see description */
#define _IONBF /* see description */
#define BUFSIZ /* see description */
#define EOF /* see description */
#define FOPEN_MAX /* see description */
#define FILENAME_MAX /* see description */
#define L_tmpnam /* see description */
#define SEEK_CUR /* see description */
#define SEEK_END /* see description */
#define SEEK_SET /* see description */
#define TMP_MAX /* see description */
#define stderr /* see description */
#define stdin /* see description */
#define stdout /* see description */

namespace std {
  int remove(const char* filename);
  int rename(const char* old_p, const char* new_p);
  FILE* tmpfile();
  char* tmpnam(char* s);
  int fclose(FILE* stream);
  int fflush(FILE* stream);
  FILE* fopen(const char* filename, const char* mode);
  FILE* freopen(const char* filename, const char* mode, FILE* stream);
  void setbuf(FILE* stream, char* buf);
  int setvbuf(FILE* stream, char* buf, int mode, size_t size);
  int fprintf(FILE* stream, const char* format, ...);
  int fscanf(FILE* stream, const char* format, ...);
  int printf(const char* format, ...);
  int scanf(const char* format, ...);
  int snprintf(char* s, size_t n, const char* format, ...);
  int sprintf(char* s, const char* format, ...);
  int sscanf(const char* s, const char* format, ...);
  int vfprintf(FILE* stream, const char* format, va_list arg);
  int vfscanf(FILE* stream, const char* format, va_list arg);
  int vprintf(const char* format, va_list arg);
  int vscanf(const char* format, va_list arg);
  int vsnprintf(char* s, size_t n, const char* format, va_list arg);
  int vsprintf(char* s, const char* format, va_list arg);
  int vsscanf(const char* s, const char* format, va_list arg);
  int fgetc(FILE* stream);
  char* fgets(char* s, int n, FILE* stream);
  int fputc(int c, FILE* stream);
  int fputs(const char* s, FILE* stream);
  int getc(FILE* stream);
  int getchar();
  int putc(int c, FILE* stream);
  int putchar(int c);
  int puts(const char* s);
  int ungetc(int c, FILE* stream);
  size_t fread(void* ptr, size_t size, size_t nmemb, FILE* stream);
  size_t fwrite(const void* ptr, size_t size, size_t nmemb, FILE* stream);
  int fgetpos(FILE* stream, fpos_t* pos);
  int fseek(FILE* stream, long int offset, int whence);
  int fsetpos(FILE* stream, const fpos_t* pos);
  long int ftell(FILE* stream);
  void rewind(FILE* stream);
  void clearerr(FILE* stream);
  int feof(FILE* stream);
  int ferror(FILE* stream);
  void perror(const char* s);
}

Notes

• NULL is also defined in the following headers:
  • <clocale>
  • <ctime>
  • <cstddef>
  • <cstring>
  • <cwchar>
  • <cstdlib>
• std::size_t is also defined in the following headers:
  • <ctime>
  • <cstddef>
  • <cstring>
  • <cwchar>
  • <cuchar> (since C++17)
  • <cstdlib>