man/man1/dhcpinfo.1

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 DHCPINFO 1 "Feb 13, 2020"
 NAME
dhcpinfo - display values of parameters received through DHCP
 SYNOPSIS
dhcpinfo [-c] [-i interface] [-n limit] [-v 4|6] code


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


 DESCRIPTION
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
parameters.
 "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, 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


 OPTIONS
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(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.


 OPERANDS
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(5).


 EXIT STATUS
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).


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


ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Committed


 SEE ALSO
 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.