fseeko(3) — Linux manual page

fseeko(3)                Library Functions Manual               fseeko(3)

NAME         top

       fseeko, ftello - seek to or report file position

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <stdio.h>

       int fseeko(FILE *stream, off_t offset, int whence);
       off_t ftello(FILE *stream);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       fseeko(), ftello():
           _FILE_OFFSET_BITS == 64 || _POSIX_C_SOURCE >= 200112L

DESCRIPTION         top

       The fseeko() and ftello() functions are identical to fseek(3) and
       ftell(3) (see fseek(3)), respectively, except that the offset
       argument of fseeko() and the return value of ftello() is of type
       off_t instead of long.

       On some architectures, both off_t and long are 32-bit types, but
       defining _FILE_OFFSET_BITS with the value 64 (before including any
       header files) will turn off_t into a 64-bit type.

RETURN VALUE         top

       On successful completion, fseeko() returns 0, while ftello()
       returns the current offset.  Otherwise, -1 is returned and errno
       is set to indicate the error.

ERRORS         top

       See the ERRORS in fseek(3).

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                            │ Attribute     │ Value   │
       ├──────────────────────────────────────┼───────────────┼─────────┤
       │ fseeko(), ftello()                   │ Thread safety │ MT-Safe │
       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS         top

       POSIX.1-2008.

HISTORY         top

       glibc 2.1.  POSIX.1-2001, SUSv2.

NOTES         top

       The declarations of these functions can also be obtained by
       defining the obsolete _LARGEFILE_SOURCE feature test macro.

SEE ALSO         top

       fseek(3)

COLOPHON         top

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Linux man-pages 6.15            2025-05-17                      fseeko(3)

Pages that refer to this page: fseek(3),  off_t(3type),  open_memstream(3),  feature_test_macros(7)

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