# Standard library header <cstdio>

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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` | 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
size_t | unsigned integer type returned by the `sizeof` operator (typedef)

### Macros

NULL | implementation-defined null pointer constant (macro constant)
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)

### 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

fgetc getc | gets a character from a file stream (function)
fgets | gets a character string from a file stream (function)
fputc putc | 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

scanf fscanf sscanf | reads formatted input from stdin, a file stream or a buffer (function)
vscanf vfscanf vsscanf (C++11)(C++11)(C++11) | reads formatted input from stdin, a file stream or a buffer using variable argument list (function)
printf fprintf sprintf snprintf (C++11) | prints formatted output to stdout, a file stream or a buffer (function)
vprintf vfprintf vsprintf vsnprintf (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)

### 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>`
  - `<cstdlib>`

### Synopsis

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

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

    namespace std {
      int remove(const char* filename);
      int rename(const char* old, const char* new);
      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);
    }

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