fclose then fopen equivalent for stdout?

[David Mathog]

A program of mine writes to a tape unit. Output can be either through
stdout or through a file opened with fopen(). When all the data is
transferred to tape the program needs to close the output stream so that
the tape driver will write a filemark on the tape. Otherwise multiple
clumps of data saved to tape would all appear to be one big file on the
tape.

When the tape unit device was explicitly opened with fopen()
that's possible: call fclose() and then for the next batch
of data fopen() the tape device again and write some more.

However when data is going through stdout like:

program /dev/nst0

is there an equivalent operation? Maybe something like this:

fputc(stdout,EO F);

or this

freopen(NULL,"w b",stdout);

?

Thanks,

David Mathog

[Jordan Abel]

2006-10-26 <eh*********@na ig.caltech.edu> ,
David Mathog wrote:

When the linux st driver receives a close operation following a write it
(the st driver) writes the filemark. The fclose() and fflush() don't
write that mark themselves. Apparently the only way to write multiple
files to tape through stdout, and to place a filemark between them,
is to use ioctl(). Even that is tricky, as doing something like:

fwrite(buffer1, BUFSIZE,1,stdou t);

fflush(stdout) before mixing stdio and low-level

ioctl( <appropriate parameters);
fwrite(buffer2, BUFSIZE,1,stdou t);

might result in the filemarks being written before all of the buffer1
data gets to the tape drive.

solved above.