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(4). 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(1M). It first contacts the DHCP client daemon dhcpagent(1M) 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(4) 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 parameters.

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(4).

The format of each individual value is determined by the data type of the option, as determined by dhcp_inittab(4). The possible data types and their formats are listed below:

Data Type Format dhcp_inittab(4) type
Unsigned Number One or more decimal digits UNUMBER8, UNUMBER16, UNUMBER32, UNUMBER64
Signed Number One or more decimal digits, optionally preceded by a minus sign SNUMBER8, SNUMBER16, SNUMBER32, SNUMBER64
IP Address Dotted-decimal notation IP
IPv6 Address Colon-separated notation IPv6
Octet The string 0x followed by a two-digit hexadecimal value OCTET
String Zero or more ASCII characters ASCII
DUID DHCP Unique Identifier text DUID
Domain Name Standard dot-separated domain name, RFC 1035 format DOMAIN

The following options are supported:

-c

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(1M) 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(1M) to set a primary interface.

The recommended practice in the dhcpagent(1M) 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:

code

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.

identifier

Mnemonic symbol for the requested DHCP parameter, as listed in dhcp_inittab(4).

The following exit values are returned:

0

Successful operation.

2

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.

3

Bad arguments.

4

The operation timed out.

6

System error (should never occur).

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Committed

dhcpagent(1M), ifconfig(1M), dhcp_inittab(4), attributes(5)

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