DHCPINFO(1) User Commands DHCPINFO(1)


dhcpinfo - display values of parameters received through DHCP


dhcpinfo [-c] [-i interface] [-n limit] [-v 4|6] code

dhcpinfo [-c] [-i interface] [-n limit] [-v 4|6] identifier


The dhcpinfo utility prints the DHCP-supplied value(s) of the parameter
requested on the command line. The parameter can be identified either by
its numeric code in the DHCP specification, or by its mnemonic
identifier, as listed in dhcp_inittab(5). This command is intended to be
used in command substitutions in the shell scripts invoked at system boot
or in event scripts as described in dhcpagent(8). It first contacts the
DHCP client daemon dhcpagent(8) to verify that DHCP has successfully
completed on the requested interface. If DHCP has successfully completed
on the requested interface, dhcpinfo retrieves the values for the
requested parameter. Parameter values echoed by dhcpinfo should not be
used without checking its exit status. See exit(1).

See dhcp_inittab(5) for the list of mnemonic identifier codes for all
DHCP parameters. See RFC 2132, DHCP Options and BOOTP Vendor Extensions
for more details on DHCPv4 parameters, and RFC 3315, Dynamic Host
Configuration Protocol for IPv6 (DHCPv6), for more details on DHCPv6

Output Format

The output from dhcpinfo consists of one or more lines of ASCII text; the
format of the output depends upon the requested parameter. The number of
values returned per line and the total number of lines output for a given
parameter are determined by the parameter's granularity and maximum
values, respectively, as defined by dhcp_inittab(5).

The format of each individual value is determined by the data type of the
option, as determined by dhcp_inittab(5). The possible data types and
their formats are listed below:

Data Type Format dhcp_inittab(5) type
Unsigned Number One or more decimal digits UNUMBER8, UNUMBER16,
Signed Number One or more decimal digits, SNUMBER8, SNUMBER16,
optionally preceded by a SNUMBER32, SNUMBER64
minus sign
IP Address Dotted-decimal notation IP
IPv6 Address Colon-separated notation IPv6
Octet The string 0x followed by a OCTET
two-digit hexadecimal value
String Zero or more ASCII characters ASCII
DUID DHCP Unique Identifier text DUID
Domain Name Standard dot-separated domain DOMAIN
name, RFC 1035 format


The following options are supported:

Displays the output in a canonical format. This format is
identical to the OCTET format with a granularity of 1.

-i interface
Specifies the interface to retrieve values for DHCP
parameters from. If this option is not specified, the
primary interface is used.

If a primary interface has not been selected for the
system by ifconfig(8) or for this command by -i, the
system automatically selects an interface to consider as
primary for the current command invocation. The
selection chooses the interface whose name sorts
lexically first, and that has DHCP parameters attached.
This selection does not affect system state. Use
ifconfig(8) to set a primary interface.

The recommended practice in the dhcpagent(8) eventhook
scripts is to specify the desired interface with -i,
rather than relying on primary selection.

For DHCPv6, the interface name used should be the name of
the physical interface, not one of the logical interfaces
created by dhcpagent.

-n limit
Limits the list of values displayed to limit lines.

-v 4|6
Specifies the DHCP version to query. Use -v 4 for DHCPv4
and -v 6 for DHCPv6.


The following operands are supported:

Numeric code for the requested DHCP parameter, as defined
by the DHCP specification. Vendor options are specified by
adding 256 to the actual vendor code for DHCPv4, and 65536
for DHCPv6.

Mnemonic symbol for the requested DHCP parameter, as listed
in dhcp_inittab(5).


The following exit values are returned:

Successful operation.

The operation was not successful. The DHCP client daemon might not
be running, the interface might have failed to configure, or no
satisfactory DHCP responses were received.

Bad arguments.

The operation timed out.

System error (should never occur).


See attributes(7) for descriptions of the following attributes:

|Interface Stability | Committed |


dhcp_inittab(5), attributes(7), dhcpagent(8), ifconfig(8)

Alexander, S., and R. Droms, RFC 2132, DHCP Options and BOOTP Vendor
Extensions, Silicon Graphics, Inc., Bucknell University, March 1997.

Droms, R. , RFC 3315, Dynamic Host Configuration Protocol for IPv6
(DHCPv6), Cisco Systems, July 2003.

Mockapetris, P.V. , RFC 1035, Domain names - implementation and
specification, ISI, November 1987.

February 13, 2020 DHCPINFO(1)