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.Dd $Mdocdate: February 13 2019 $
.Dt HTONL 3
.Os
.Sh NAME
.Nm htonl ,
.Nm htons ,
.Nm ntohl ,
.Nm ntohs
.Nd convert values between host and network byte orderings
.Sh SYNOPSIS
.In arpa/inet.h
.Ft uint32_t
.Fn htonl "uint32_t host32"
.Ft uint16_t
.Fn htons "uint16_t host16"
.Ft uint32_t
.Fn ntohl "uint32_t net32"
.Ft uint16_t
.Fn ntohs "uint16_t net16"
.Sh DESCRIPTION
These routines convert 16 and 32-bit quantities between different
byte orderings.
.Pp
The
.Fn htonl
and
.Fn htons
functions convert quantities from host to network byte order while the
.Fn ntohl
and
.Fn ntohs
functions convert in the other direction.
.Pp
The last letter
.Pf ( Sq s
or
.Sq l )
is a mnemonic
for the traditional names for such quantities,
.Li short
and
.Li long ,
respectively.
Today, the C concept of
.Li short
and
.Li long
integers need not coincide with this traditional misunderstanding.
On machines which have a byte order which is the same as the network
order, routines are defined as null macros.
.Pp
These routines are most often used in conjunction with Internet
addresses and ports as returned by
.Xr gethostbyname 3
and
.Xr getservent 3 .
.Sh SEE ALSO
.Xr gethostbyname 3 ,
.Xr getservent 3 ,
.Xr htobe64 3
.Sh STANDARDS
The
.Fn htonl ,
.Fn htons ,
.Fn ntohl ,
and
.Fn ntohs
functions conform to
.St -p1003.1 .
.Sh HISTORY
These functions appeared in
.Bx 4.2 .
.Sh BUGS
On the alpha, amd64, i386, and some mips and arm architectures,
bytes are handled backwards from most everyone else in the world.
This is not expected to be fixed in the near future.