NAME

       sg_readcap - send SCSI READ CAPACITY command

SYNOPSIS

       sg_readcap [--16] [--brief] [--help] [--hex] [--lba=LBA] [--long] [--pmi] [--raw] [--verbose] [--version]
       DEVICE

       sg_readcap [-16] [-b] [-h] [-H] [-lba=LBA] [-pmi] [-r] [-v] [-V] DEVICE

DESCRIPTION

       The  normal  action  of  the SCSI READ CAPACITY command is to fetch the number of blocks (and block size)
       from the DEVICE.

       The SCSI READ CAPACITY command (both 10 and 16 byte cdbs) actually yield the block address  of  the  last
       block  and  the block size. The number of blocks is thus one plus the block address of the last block (as
       blocks are counted origin zero (i.e. starting at block zero)). This is the source of many  "off  by  one"
       errors.

       The  READ  CAPACITY(16)  response  provides  additional  information  not  found in the READ CAPACITY(10)
       response. This includes protection and logical block provisioning information, plus the number of logical
       blocks per physical block. So even though the media size may not exceed what READ CAPACITY(10) can  show,
       it  may  still  be  useful  to  examine  the response to READ CAPACITY(16). Sadly there are horrible SCSI
       command set implementations in the wild that crash when the READ CAPACITY(16) command is sent to them.

       Device capacity is the product of the number of blocks by the block  size.   This  utility  outputs  this
       figure in bytes, MiB (1048576 bytes per MiB) and GB (1000000000 bytes per GB).

       If  sg_readcap is called without the --long option then the 10 byte cdb version (i.e. READ CAPACITY (10))
       is sent to the DEVICE. If the number of blocks in the response is reported as 0xffffffff (i.e.  (2**32  -
       1)  )  and  the  --hex  option  has not been given, then READ CAPACITY (16) is called and its response is
       output.

       This utility supports two command line syntaxes, the preferred one is shown first  in  the  synopsis  and
       explained  in  this  section. A later section on the old command line syntax outlines the second group of
       options.

OPTIONS

       Arguments to long options are mandatory for short options as well.

       --16   Use the 16 byte cdb variant of the READ CAPACITY command. See the '--long'  option.   -b,  --brief
              outputs  two  hex  numbers (prefixed with '0x' and space separated) to stdout. The first number is
              the maximum number of blocks on the device (which is one plus  the  lba  of  the  last  accessible
              block).  The  second  number  is the size in bytes of each block. If the operation fails then "0x0
              0x0" is written to stdout.

       -h, --help
              print out the usage message then exit.

       -H, --hex
              output the response to the READ CAPACITY command (either the 10 or 16 byte cdb variant)  in  ASCII
              hexadecimal on stdout.

       -L, --lba=LBA
              used  in  conjunction  with  --pmi option. This variant of READ CAPACITY will yield the last block
              address after LBA prior to a delay. For a disk, given a LBA it yields the highest  numbered  block
              on  the  same  cylinder  (i.e. before the heads need to move). LBA is assumed to be decimal unless
              prefixed by "0x" or it has a trailing "h". Defaults to 0.  This option was made obsolete in  SBC-3
              revision 26.

       -l, --long
              Use the 16 byte cdb variant of the READ CAPACITY command. The default action is to use the 10 byte
              cdb  variant  which  limits  the  maximum  block  address  to (2**32 - 2). When a 10 byte cdb READ
              CAPACITY command is used on a device whose size  is  too  large  then  a  last  block  address  of
              0xffffffff is returned (if the device complies with SBC-2 or later).

       -O, --old
              switch to older style options.

       -p, --pmi
              partial  medium  indicator:  for  finding  the  next  block address prior to some delay (e.g. head
              movement). In the absence of this option, the total number of blocks and the  block  size  of  the
              device  are  output.  Used in conjunction with the --lba=LBA option. This option was made obsolete
              in SBC-3 revision 26.

       -r, --raw
              output response in binary to stdout.

       -v, --verbose
              increase level of verbosity. Can be used multiple times.

       -V, --version
              outputs version string then exits.

NOTES

       In the 2.4 series of Linux kernels the DEVICE must be a SCSI generic (sg) device. In the 2.6 series block
       devices (e.g. SCSI disks and DVD drives) can also be specified. For  example  "sg_readcap  /dev/sda"  and
       "sg_readcap /dev/hdd" (if /dev/hdd is a ATAPI CD/DVD device) will work in the 2.6 series kernels.

EXIT STATUS

       The exit status of sg_readcap is 0 when it is successful. Otherwise see the sg3_utils(8) man page.

OLDER COMMAND LINE OPTIONS

       The  options  in this section were the only ones available prior to sg3_utils version 1.23 . In sg3_utils
       version 1.23 and later these older options can be  selected  by  either  setting  the  SG3_UTILS_OLD_OPTS
       environment variable or using '--old' (or '-O) as the first option.

       -16    Use  the  16  byte  cdb  variant  of  the READ CAPACITY command.  Equivalent to --long in the main
              description.

       -b     utility outputs two hex numbers (prefixed with '0x' and space  separated)  to  stdout.  The  first
              number  is  the  maximum  number  of  blocks  on the device (which is one plus the lba of the last
              accessible block). The second number is the size of each block. If the operation fails  then  "0x0
              0x0" is written to stdout.  Equivalent to --brief in the main description.

       -h     output  the  usage  message  then  exit.  Giving the -? option also outputs the usage message then
              exits.

       -H     output the response to the READ CAPACITY command (either the 10 or 16 byte cdb variant)  in  ASCII
              hexadecimal on stdout.

       -lba=LBA
              used  in  conjunction  with  -pmi  option. This variant of READ CAPACITY will yield the last block
              address after LBA prior to a delay.  Equivalent to --lba=LBA in the main description.

       -N     switch to the newer style options.

       -pmi   partial medium indicator: for finding the next block  address  prior  to  some  delay  (e.g.  head
              movement).  In  the  absence  of this switch, the total number of blocks and the block size of the
              device are output.  Equivalent to --pmi in the main description.

       -r     output response in binary (to stdout).

       -v     verbose: print out cdb of issued commands prior to execution. '-vv' and '-vvv' are  also  accepted
              yielding greater verbosity.

       -V     outputs version string then exits.

AUTHORS

       Written by Douglas Gilbert

COPYRIGHT

       Copyright © 1999-2013 Douglas Gilbert
       This  software is distributed under the GPL version 2. There is NO warranty; not even for MERCHANTABILITY
       or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO

       sg_inq(sg3_utils)

sg3_utils-1.36                                      May 2012                                       SG_READCAP(8)