stdio.h(0p) — Linux manual page


stdio.h(0P)             POSIX Programmer's Manual            stdio.h(0P)

PROLOG         top

       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         top

       stdio.h — standard buffered input/output

SYNOPSIS         top

       #include <stdio.h>

DESCRIPTION         top

       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.1‐2017, 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()

       L_tmpnam      Maximum size of character array to hold tmpnam()

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

       _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

       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:

                     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

       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,
           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.


       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         top

       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.



SEE ALSO         top

       stdarg.h(0p), stddef.h(0p), sys_types.h(0p)

       The System Interfaces volume of POSIX.1‐2017, Section 2.2, The
       Compilation Environment, clearerr(3p), ctermid(3p), fclose(3p),
       fdopen(3p), feof(3p), ferror(3p), fflush(3p), fgetc(3p),
       fgetpos(3p), fgets(3p), fileno(3p), flockfile(3p), fmemopen(3p),
       fopen(3p), fprintf(3p), fputc(3p), fputs(3p), fread(3p),
       freopen(3p), fscanf(3p), fseek(3p), fsetpos(3p), ftell(3p),
       fwrite(3p), getc(3p), getchar(3p), getc_unlocked(3p),
       getdelim(3p), getopt(3p), gets(3p), open_memstream(3p),
       pclose(3p), perror(3p), popen(3p), putc(3p), putchar(3p),
       puts(3p), remove(3p), rename(3p), rewind(3p), setbuf(3p),
       setvbuf(3p), stdin(3p), system(3p), tempnam(3p), tmpfile(3p),
       tmpnam(3p), ungetc(3p), vfprintf(3p), vfscanf(3p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  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 .

       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 .

IEEE/The Open Group               2017                       stdio.h(0P)

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