Tribblix: manual page: dhcpinfo.1

DHCPINFO(1) User Commands DHCPINFO(1)

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, 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

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