Standard library header <stdio.h>

This header is part of input/output library, providing generic file operation support and supplies I/O functions that work with narrow characters.

Types

FILE	object type, capable of holding all information needed to control a C I/O stream (typedef)
fpos_t	non-array complete object type, capable of uniquely specifying a position and multibyte parser state in a file (typedef)

Predefined standard streams

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)

Functions

File access
fopenfopen_s (C11)	opens a file (function)
freopenfreopen_s (C11)	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)
getsgets_s (removed in C11)(C11)	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 character
scanffscanfsscanfscanf_sfscanf_ssscanf_s (C11)(C11)(C11)	reads formatted input from stdin, a file stream or a buffer (function)
vscanfvfscanfvsscanfvscanf_svfscanf_svsscanf_s (C99)(C99)(C99)(C11)(C11)(C11)	reads formatted input from stdin, a file stream or a buffer using variable argument list (function)
printffprintfsprintfsnprintfprintf_sfprintf_ssprintf_ssnprintf_s (C99)(C11)(C11)(C11)(C11)	prints formatted output to stdout, a file stream or a buffer (function)
vprintfvfprintfvsprintfvsnprintfvprintf_svfprintf_svsprintf_svsnprintf_s (C99)(C11)(C11)(C11)(C11)	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)
tmpfiletmpfile_s (C11)	returns a pointer to a temporary file (function)
tmpnamtmpnam_s (C11)	returns a unique filename (function)

Macro constants

EOF	integer constant expression of type int and negative value (macro constant)
FOPEN_MAX	maximum 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)

_PRINTF_NAN_LEN_MAX (C23)

the maximum number of characters output for any (possibly negated) NaN value (macro constant)

BUFSIZ	size of the buffer used by setbuf (macro constant)
_IOFBF_IOLBF_IONBF	indicates the buffering mode (fully buffered / line buffered / unbuffered) to be set by setvbuf (macro constant)
SEEK_SETSEEK_CURSEEK_END	indicates the offset origin (beginning / current position / end) to be used by fseek (macro constant)
TMP_MAXTMP_MAX_S (C11)	maximum number of unique filenames that can be generated by tmpnam / tmpnam_s (macro constant)
L_tmpnamL_tmpnam_s (C11)	size needed for an array of char to hold the result of tmpnam / tmpnam_s (macro constant)

Synopsis

#define __STDC_VERSION_STDIO_H__ 202311L

typedef /* see description */ FILE;
typedef /* see description */ size_t;
typedef /* see description */ FILE;
typedef /* see description */ fpos_t;

#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 stdin        /* see description */
#define stdout       /* see description */
#define stderr       /* see description */

#define _PRINTF_NAN_LEN_MAX /* see description */

int remove(const char* filename);
int rename(const char* old, const char* new);
FILE* tmpfile(void);
char* tmpnam(char* s);
int fclose(FILE* stream);
int fflush(FILE* stream);
FILE* fopen(const char* restrict filename, const char* restrict mode);
FILE* freopen(const char* restrict filename, const char* restrict mode,
FILE* restrict stream);
void setbuf(FILE* restrict stream, char* restrict buf);
int setvbuf(FILE* restrict stream, char* restrict buf, int mode, size_t size);
int printf(const char* restrict format, ...);
int scanf(const char* restrict format, ...);
int snprintf(char* restrict s, size_t n, const char* restrict format, ...);
int sprintf(char* restrict s, const char* restrict format, ...);
int sscanf(const char* restrict s, const char* restrict format, ...);
int vfprintf(FILE* restrict stream, const char* restrict format, va_list arg);
int vfscanf(FILE* restrict stream, const char* restrict format, va_list arg);
int vprintf(const char* restrict format, va_list arg);
int vscanf(const char* restrict format, va_list arg);
int vsnprintf(char* restrict s, size_t n, const char* restrict format, va_list arg);
int vsprintf(char* restrict s, const char* restrict format, va_list arg);
int vsscanf(const char* restrict s, const char* restrict format, va_list arg);
int fgetc(FILE* stream);
char* fgets(char* restrict s, int n, FILE* restrict stream);
int fputc(int c, FILE* stream);
int fputs(const char* restrict s, FILE* restrict stream);
int getc(FILE* stream);
int getchar(void);
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* restrict ptr, size_t size, size_t nmemb,
FILE* restrict stream);
size_t fwrite(const void* restrict ptr, size_t size, size_t nmemb,
FILE* restrict stream);
int fgetpos(FILE* restrict stream, fpos_t* restrict 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);
int fprintf(FILE* restrict stream, const char* restrict format, ...);
int fscanf(FILE* restrict stream, const char* restrict format, ...);

Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines __STDC_WANT_LIB_EXT1__ before any inclusion of <stdio.h>:

#if defined(__STDC_WANT_LIB_EXT1__)

#define L_tmpnam_s /* see description */
#define TMP_MAX_S  /* see description */

typedef /* see description */ errno_t;
typedef /* see description */ rsize_t;

errno_t tmpfile_s(FILE* restrict* restrict streamptr);
errno_t tmpnam_s(char* s, rsize_t maxsize);
errno_t fopen_s(FILE* restrict* restrict streamptr,
const char* restrict filename, const char* restrict mode);
errno_t freopen_s(FILE* restrict* restrict newstreamptr,
const char* restrict filename, const char* restrict mode,
FILE* restrict stream);
int fprintf_s(FILE* restrict stream, const char* restrict format, ...);
int fscanf_s(FILE* restrict stream, const char* restrict format, ...);
int printf_s(const char* restrict format, ...);
int scanf_s(const char* restrict format, ...);
int snprintf_s(char* restrict s, rsize_t n, const char* restrict format, ...);
int sprintf_s(char* restrict s, rsize_t n, const char* restrict format, ...);
int sscanf_s(const char* restrict s, const char* restrict format, ...);
int vfprintf_s(FILE* restrict stream, const char* restrict format, va_list arg);
int vfscanf_s(FILE* restrict stream, const char* restrict format, va_list arg);
int vprintf_s(const char* restrict format, va_list arg);
int vscanf_s(const char* restrict format, va_list arg);
int vsnprintf_s(char* restrict s, rsize_t n, const char* restrict format, va_list arg);
int vsprintf_s(char* restrict s, rsize_t n, const char* restrict format, va_list arg);
int vsscanf_s(const char* restrict s, const char* restrict format, va_list arg);
char* gets_s(char* s, rsize_t n);
#endif