<stdio.h>

NAME

stdio.h - standard buffered input/output

SYNOPSIS

#include <stdio.h>

DESCRIPTION

^[] [Option Start] Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the System Interfaces volume of IEEE Std 1003.1-2001, Section 2.2, The Compilation Environment) to enable the visibility of these symbols in this header. [Option End]

The <stdio.h> header shall define the following macros as positive integer constant expressions:

BUFSIZ

Size of <stdio.h> buffers.

_IOFBF

Input/output fully buffered.

_IOLBF

Input/output line buffered.

_IONBF

Input/output unbuffered.

L_ctermid

^[] [Option Start] Maximum size of character array to hold ctermid() output. [Option End]

L_tmpnam

Maximum size of character array to hold tmpnam() output.

SEEK_CUR

Seek relative to current position.

SEEK_END

Seek relative to end-of-file.

SEEK_SET

Seek relative to start-of-file.

The following macros shall be defined as positive integer constant expressions which denote implementation limits:

{FILENAME_MAX}

Maximum size in bytes of the longest filename string that the implementation guarantees can be opened.

{FOPEN_MAX}

Number of streams which the implementation guarantees can be open simultaneously. The value is at least eight.

{TMP_MAX}

Minimum number of unique filenames generated by tmpnam(). Maximum number of times an application can call tmpnam() reliably. The value of {TMP_MAX} is at least 25. ^[] [Option Start] On XSI-conformant systems, the value of {TMP_MAX} is at least 10000. [Option End]

The following macro name shall be defined as a negative integer constant expression:

EOF

End-of-file return value.

The following macro name shall be defined as a null pointer constant:

NULL

Null pointer.

The following macro name shall be defined as a string constant:

P_tmpdir

^[] [Option Start] Default directory prefix for tempnam().

The following shall be defined as expressions of type "pointer to FILE" that point to the FILE objects associated, respectively, with the standard error, input, and output streams:

stderr

Standard error output stream.

stdin

Standard input stream.

stdout

Standard output stream.

The following data types shall be defined through typedef:

FILE

A structure containing information about a file.

fpos_t

A non-array type containing all information needed to specify uniquely every position within a file.

va_list

^[] [Option Start] As described in <stdarg.h>. [Option End]

size_t

As described in <stddef.h>.

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

void clearerr(FILE *);
[][Option Start]
char *ctermid(char *);
[Option End]
int fclose(FILE *);
[][Option Start]
FILE *fdopen(int, const char *);
[Option End]
int feof(FILE *);
int ferror(FILE *);
int fflush(FILE *);
int fgetc(FILE *);
int fgetpos(FILE *restrict, fpos_t *restrict);
char *fgets(char *restrict, int, FILE *restrict);
[][Option Start]
int fileno(FILE *);
[Option End]
[][Option Start]
void flockfile(FILE *);
[Option End]
FILE *fopen(const char *restrict, const char *restrict);
int fprintf(FILE *restrict, const char *restrict, ...);
int fputc(int, FILE *);
int fputs(const char *restrict, FILE *restrict);
size_t fread(void *restrict, size_t, size_t, FILE *restrict);
FILE *freopen(const char *restrict, const char *restrict,
 FILE *restrict);
int fscanf(FILE *restrict, const char *restrict, ...);
int fseek(FILE *, long, int);
[][Option Start]
int fseeko(FILE *, off_t, int);
[Option End]
int fsetpos(FILE *, const fpos_t *);
long ftell(FILE *);
[][Option Start]
off_t ftello(FILE *);
[Option End]
[][Option Start]
int ftrylockfile(FILE *);
void funlockfile(FILE *);
[Option End]
size_t fwrite(const void *restrict, size_t, size_t, FILE *restrict);
int getc(FILE *);
int getchar(void);
[][Option Start]
int getc_unlocked(FILE *);
int getchar_unlocked(void);
[Option End]
char *gets(char *);
[][Option Start]
int pclose(FILE *);
[Option End]
void perror(const char *);
[][Option Start]
FILE *popen(const char *, const char *);
[Option End]
int printf(const char *restrict, ...);
int putc(int, FILE *);
int putchar(int);
[][Option Start]
int putc_unlocked(int, FILE *);
int putchar_unlocked(int);
[Option End]
int puts(const char *);
int remove(const char *);
int rename(const char *, const char *);
void rewind(FILE *);
int scanf(const char *restrict, ...);
void setbuf(FILE *restrict, char *restrict);
int setvbuf(FILE *restrict, char *restrict, int, size_t);
int snprintf(char *restrict, size_t, const char *restrict, ...);
int sprintf(char *restrict, const char *restrict, ...);
int sscanf(const char *restrict, const char *restrict, int ...);
[][Option Start]
char *tempnam(const char *, const char *);
[Option End]
FILE *tmpfile(void);
char *tmpnam(char *);
int ungetc(int, FILE *);
int vfprintf(FILE *restrict, const char *restrict, va_list);
int vfscanf(FILE *restrict, const char *restrict, va_list);
int vprintf(const char *restrict, va_list);
int vscanf(const char *restrict, va_list);
int vsnprintf(char *restrict, size_t, const char *restrict,
 va_list);
int vsprintf(char *restrict, const char *restrict, va_list);
int vsscanf(const char *restrict, const char *restrict,
 va_list arg);

^[] [Option Start] Inclusion of the <stdio.h> header may also make visible all symbols from <stddef.h>. [Option End]

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

<stdarg.h>, <stddef.h>, <sys/types.h>, the System Interfaces volume of IEEE Std 1003.1-2001, clearerr(), ctermid(), fclose(), fdopen(), fgetc(), fgetpos(), ferror(), feof(), fflush(), fgets(), fileno(), flockfile(), fopen(), fputc(), fputs(), fread(), freopen(), fseek(), fsetpos(), ftell(), fwrite(), getc(), getc_unlocked(), getwchar(), getchar(), getopt(), gets(), pclose(), perror(), popen(), printf(), putc(), putchar(), puts(), putwchar(), remove(), rename(), rewind(), scanf(), setbuf(), setvbuf(), sscanf(), stdin, system(), tempnam(), tmpfile(), tmpnam(), ungetc(), vfscanf(), vscanf(), vprintf(), vsscanf()

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 5

The DESCRIPTION is updated for alignment with the POSIX Threads Extension.

Large File System extensions are added.

The constant L_cuserid and the external variables optarg, opterr, optind, and optopt are marked as extensions and LEGACY.

The cuserid() and getopt() functions are marked LEGACY.

Issue 6

The constant L_cuserid and the external variables optarg, opterr, optind, and optopt are removed as they were previously marked LEGACY.

The cuserid(), getopt(), and getw() functions are removed as they were previously marked LEGACY.

Several functions are marked as part of the Thread-Safe Functions option.

This reference page is updated to align with the ISO/IEC 9899:1999 standard. Note that the description of the fpos_t type is now explicitly updated to exclude array types.

Extensions beyond the ISO C standard are marked.