method

sysseek

v1_8_6_287 - Show latest stable - 0 notes - Class: IO

sysseek(...) public

Seeks to a given offset in the stream according to the value of whence (see IO#seek for values of whence). Returns the new offset into the file.

   f = File.new("testfile")
   f.sysseek(-13, IO::SEEK_END)   #=> 53
   f.sysread(10)                  #=> "And so on."

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/*
 *  call-seq:
 *     ios.sysseek(offset, whence=SEEK_SET)   => integer
 *  
 *  Seeks to a given <i>offset</i> in the stream according to the value
 *  of <i>whence</i> (see <code>IO#seek</code> for values of
 *  <i>whence</i>). Returns the new offset into the file.
 *     
 *     f = File.new("testfile")
 *     f.sysseek(-13, IO::SEEK_END)   #=> 53
 *     f.sysread(10)                  #=> "And so on."
 */

static VALUE
rb_io_sysseek(argc, argv, io)
    int argc;
    VALUE *argv;
    VALUE io;
{
    VALUE offset, ptrname;
    int whence = SEEK_SET;
    OpenFile *fptr;
    off_t pos;

    if (rb_scan_args(argc, argv, "11", &offset, &ptrname) == 2) {
        whence = NUM2INT(ptrname);
    }
    pos = NUM2OFFT(offset);
    GetOpenFile(io, fptr);
    if ((fptr->mode & FMODE_READABLE) && READ_DATA_BUFFERED(fptr->f)) {
        rb_raise(rb_eIOError, "sysseek for buffered IO");
    }
    if ((fptr->mode & FMODE_WRITABLE) && (fptr->mode & FMODE_WBUF)) {
        rb_warn("sysseek for buffered IO");
    }
    pos = lseek(fileno(fptr->f), pos, whence);
    if (pos == -1) rb_sys_fail(fptr->path);
    clearerr(fptr->f);

    return OFFT2NUM(pos);
}

sysseek

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