STIOCHGP

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This IOCTL command sets the current block size. A block size of zero is a variable block. Any other value is a fixed block.

An example of the STIOCHGP command is

#include <sys/Atape.h>

  struct stchgp stchgp;

  stchgp.st_blksize = 512;

  if (ioctl(tapefd,STIOCHGP,&stchgp)<0)
    {
    printf("IOCTL failure. errno=%d",errno);
    exit(errno);
    }