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PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       stdio.h — standard buffered input/output

SYNOPSIS

       #include <stdio.h>

DESCRIPTION

       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 POSIX.1‐2008, Section 2.2, The Compilation Environment) to enable the visibility
       of these symbols in this header.

       The <stdio.h> header shall define the following data types 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.

       off_t         As described in <sys/types.h>.

       size_t        As described in <stddef.h>.

       ssize_t       As described in <sys/types.h>.

       va_list       As described in <stdarg.h>.

       The  <stdio.h>  header  shall  define  the  following macros which shall expand to integer
       constant expressions:

       BUFSIZ        Size of <stdio.h> buffers.  This shall expand to a positive value.

       L_ctermid     Maximum size of character array to hold ctermid() output.

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

       The <stdio.h> header shall define the following  macros  which  shall  expand  to  integer
       constant expressions with distinct values:

       _IOFBF        Input/output fully buffered.

       _IOLBF        Input/output line buffered.

       _IONBF        Input/output unbuffered.

       The  <stdio.h>  header  shall  define  the  following macros which shall expand to integer
       constant expressions with distinct values:

       SEEK_CUR      Seek relative to current position.

       SEEK_END      Seek relative to end-of-file.

       SEEK_SET      Seek relative to start-of-file.

       The <stdio.h> header shall define the following  macros  which  shall  expand  to  integer
       constant expressions denoting implementation limits:

       {FILENAME_MAX}
                     Maximum  size  in  bytes  of  the  longest  pathname 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.

                     On XSI-conformant systems, the value of {TMP_MAX} is at least 10000.

       The  <stdio.h>  header  shall  define the following macro which shall expand to an integer
       constant expression with type int and a negative value:

       EOF           End-of-file return value.

       The <stdio.h> header shall define NULL as described in <stddef.h>.

       The <stdio.h> header shall define the following macro  which  shall  expand  to  a  string
       constant:

       P_tmpdir      Default directory prefix for tempnam().

       The  <stdio.h>  header shall define the following macros which shall expand to 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  shall be declared as functions and may also be defined as macros. Function
       prototypes shall be provided.

           void     clearerr(FILE *);
           char    *ctermid(char *);
           int      dprintf(int, const char *restrict, ...)
           int      fclose(FILE *);
           FILE    *fdopen(int, const char *);
           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);
           int      fileno(FILE *);
           void     flockfile(FILE *);
           FILE    *fmemopen(void *restrict, size_t, const char *restrict);
           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);
           int      fseeko(FILE *, off_t, int);
           int      fsetpos(FILE *, const fpos_t *);
           long     ftell(FILE *);
           off_t    ftello(FILE *);
           int      ftrylockfile(FILE *);
           void     funlockfile(FILE *);
           size_t   fwrite(const void *restrict, size_t, size_t, FILE *restrict);
           int      getc(FILE *);
           int      getchar(void);
           int      getc_unlocked(FILE *);
           int      getchar_unlocked(void);
           ssize_t  getdelim(char **restrict, size_t *restrict, int,
                        FILE *restrict);
           ssize_t  getline(char **restrict, size_t *restrict, FILE *restrict);
           char    *gets(char *);
           FILE    *open_memstream(char **, size_t *);
           int      pclose(FILE *);
           void     perror(const char *);
           FILE    *popen(const char *, const char *);
           int      printf(const char *restrict, ...);
           int      putc(int, FILE *);
           int      putchar(int);
           int      putc_unlocked(int, FILE *);
           int      putchar_unlocked(int);
           int      puts(const char *);
           int      remove(const char *);
           int      rename(const char *, const char *);
           int      renameat(int, const char *, int, 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, ...);
           char    *tempnam(const char *, const char *);
           FILE    *tmpfile(void);
           char    *tmpnam(char *);
           int      ungetc(int, FILE *);
           int      vdprintf(int, const char *restrict, va_list);
           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);

       Inclusion of the <stdio.h> header may also make visible all symbols from <stddef.h>.

       The following sections are informative.

APPLICATION USAGE

       Since standard I/O streams may use an  underlying  file  descriptor  to  access  the  file
       associated with a stream, application developers need to be aware that {FOPEN_MAX} streams
       may not be available if file descriptors are being used  to  access  files  that  are  not
       associated with streams.

RATIONALE

       There  is  a conflict between the ISO C standard and the POSIX definition of the {TMP_MAX}
       macro that is addressed by  ISO/IEC 9899:1999  standard,  Defect  Report  336.  The  POSIX
       standard  is  in  alignment  with  the public record of the response to the Defect Report.
       This change has not yet been published as part of the ISO C standard.

FUTURE DIRECTIONS

       None.

SEE ALSO

       <stdarg.h>, <stddef.h>, <sys_types.h>

       The System Interfaces volume of POSIX.1‐2008, Section 2.2, The Compilation Environment,
       clearerr(), ctermid(), fclose(), fdopen(), feof(), ferror(), fflush(), fgetc(), fgetpos(),
       fgets(), fileno(), flockfile(), fmemopen(), fopen(), fprintf(), fputc(), fputs(), fread(),
       freopen(), fscanf(), fseek(), fsetpos(), ftell(), fwrite(), getc(), getchar(),
       getc_unlocked(), getdelim(), getopt(), gets(), open_memstream(), pclose(), perror(),
       popen(), putc(), putchar(), puts(), remove(), rename(), rewind(), setbuf(), setvbuf(),
       stdin, system(), tempnam(), tmpfile(), tmpnam(), ungetc(), vfprintf(), vfscanf()

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1,  2013  Edition,  Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013  by  the
       Institute  of  Electrical  and  Electronics  Engineers,  Inc and The Open Group.  (This is
       POSIX.1-2008 with the  2013  Technical  Corrigendum  1  applied.)  In  the  event  of  any
       discrepancy  between  this  version and the original IEEE and The Open Group Standard, the
       original IEEE and The Open Group Standard is the referee document. The  original  Standard
       can be obtained online at http://www.unix.org/online.html .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .