man sg_timestamp (8): report or set timestamp on SCSI device

SYNOPSIS

sg_timestamp [--help] [--milliseconds=MS] [--origin] [--raw] [--readonly] [--seconds=SEC] [--srep] [--verbose] [--version] DEVICE

DESCRIPTION

Sends a SCSI REPORT TIMESTAMP or SET TIMESTAMP command to the DEVICE. These commands are found in the SPC-5 draft standard revision 7 (spc5r07.pdf).

If either the --milliseconds=MS or --seconds=SEC option is given (and both can't be given) then the SET TIMESTAMP command is sent; otherwise the REPORT TIMESTAMP command is sent.

The timestamp is sent and received from the DEVICE as the number of milliseconds since the epoch of 1970-01-01 00:00:00 UTC and is held in a 48 bit unsigned integer. That same epoch is used by Unix machines, but they usually hold the number of seconds since that epoch. The Unix date command and especally its "+%s" format is useful in converting to and from timestamps and more humanly readable forms. See the EXAMPLES section below.

OPTIONS

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

-h, --help: output the usage message then exit.
-m, --milliseconds=MS: where MS is the number of milliseconds since 1970-01-01 00:00:00 UTC to set in the DEVICE with the SCSI SET TIMESTAMP command.
-o, --origin: the REPORT TIMESTAMP returned parameter data contains a "timestamp origin" field. When this option is given, that field is decoded and printed out before the timestamp value is output. The default action (i.e. when the option is not given) is not to print out this decoded field.
-r, --raw: output the SCSI REPORT TIMESTAMP response (i.e. the data-out buffer) in binary (to stdout). Note that the --origin and --srep options are ignored when this option is given. Also all error and verbose messages are output to stderr.
-R, --readonly: open the DEVICE read-only. The default action is to open the DEVICE read-write.
-s, --seconds=SEC: where SEC is the number of seconds since 1970-01-01 00:00:00 UTC to set in the DEVICE with the SCSI SET TIMESTAMP command. SEC is multiplied by 1000 before being used in the SET TIMESTAMP command.
-S, --srep: report the number of seconds since 1970-01-01 00:00:00 UTC. This is done by dividing by 1000 the value returned by the SCSI REPORT TIMESTAMP command.
-v, --verbose: increase the level of verbosity, (i.e. debug output).
-V, --version: print the version string and then exit.

EXIT STATUS

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

NOTES

The TCMOS and the SCSIP bits in the Control extension mode page (see sdparm) modify the actions of the timestamp held by a DEVICE.

Currently only the "Utilization usage rate based on date and time" parameters within the Utilization log page (sbc4r09.pdf) use timestamps. See the sg_logs utility. Vendor specific commands and pages may also be using timestamps.

EXAMPLES

On Unix machines (e.g. Linux, FreeBSD and Solaris) the date command is useful when working with timestamps.

To fetch the timestamp from a DEVICE and display it in a humanly readable form the following could be used:

   # sg_timestamp -S /dev/sdb
1448993950

   # date --date="@1448993950"
Tue Dec 1 13:19:10 EST 2015

   # date -R --date="@1448993950"
Tue, 01 Dec 2015 13:19:10 -0500

The latter two date commands show different forms of the same date (i.e. 1448993950 seconds since 1970-01-01 00:00:00 UTC). The sg_timestamp and date commands can be combined using backquotes:

# date -R --date="@`sg_timestamp -S /dev/sdc`"
Wed, 16 Dec 2015 20:12:59 -0500

To set the timestamp on the DEVICE to now (approximately) the following could be used:

# date +%s
1448993955

# sg_timestamp --seconds=1448993955 /dev/sdb

Those two command lines could be combined into one by using backquotes:

# sg_timestamp --seconds=`date +%s` /dev/sdb

AUTHORS

Written by Douglas Gilbert.

REPORTING BUGS

Report bugs to <dgilbert at interlog dot com>.