FSEEK(3) BSD Programmer's Manual FSEEK(3)
fgetpos, fseek, fseeko, fsetpos, ftell, ftello, rewind - reposition a stream
#include <stdio.h> int fgetpos(FILE *stream, fpos_t *pos); int fseek(FILE *stream, long offset, int whence); int fseeko(FILE *stream, off_t offset, int whence); int fsetpos(FILE *stream, const fpos_t *pos); long ftell(FILE *stream); off_t ftello(FILE *stream); void rewind(FILE *stream);
The fseek() function sets the file position indicator for the stream pointed to by stream. The new position, measured in bytes, is obtained by adding offset bytes to the position specified by whence. If whence is set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the start of the file, the current position indicator, or end-of-file, respective- ly. A successful call to the fseek() function clears the end-of-file in- dicator for the stream and undoes any effects of the ungetc(3) function on the same stream. The fseeko() function is identical to fseek() except that it takes an off_t as its offset. The ftell() function obtains the current value of the file position indi- cator for the stream pointed to by stream. The ftello() function is identical to ftell() except that its return value is of type off_t. The rewind() function sets the file position indicator for the stream pointed to by stream to the beginning of the file. It is equivalent to: (void)fseek(stream, 0L, SEEK_SET) except that the error indicator for the stream is also cleared (see clearerr(3)). The fgetpos() and fsetpos() functions are alternate interfaces equivalent to ftell() and fseek() (with whence set to SEEK_SET), setting and storing the current value of the file offset into or from the object referenced by pos. On some (non-UNIX) systems an "fpos_t" object may be a complex object and these routines may be the only way to portably reposition a text stream.
The rewind() function returns no value. Upon successful completion, fget- pos(), fseek(), fseeko(), fsetpos() return 0 and ftell() and ftello() re- turn the current offset. Otherwise, fseek() and fseeko() return -1 and the others return a non-zero value and the global variable errno is set to indicate the error.
[EBADF] The stream specified is not a seekable stream. [EINVAL] The whence argument to fseek() was not SEEK_SET, SEEK_END, or SEEK_CUR. The functions fgetpos(), fseek(), fseeko(), fsetpos(), ftell(), and ftel- lo() may also fail and set errno for any of the errors specified for the routines fflush(3), fstat(2), lseek(2), and malloc(3).
The fgetpos(), fsetpos(), fseek(), ftell(), and rewind() functions con- form to ANSI X3.159-1989 ("ANSI C") and X/Open Portability Guide Issue 4 ("XPG4"). The fseeko() and ftello() functions conform to X/Open Portability Guide Issue 4 ("XPG4"). MirOS BSD #10-current February 21, 2000 1
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