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ADDR2ASCII (3) | C library functions | Unix Manual Pages | :man

NAME

addr2ascii, ascii2addr - Generic address formatting routines

CONTENTS

Library
Synopsis
Description
Return Values
Examples
Errors
See Also
History
Authors
Bugs

LIBRARY


.Lb libc

SYNOPSIS


.In arpa/inet.h "char *" addr2ascii "int af" "const void *addrp" "int len" "char *buf" int ascii2addr "int af" "const char *ascii" "void *result"

DESCRIPTION

The routines addr2ascii and ascii2addr are used to convert network addresses between binary form and a printable form appropriate to the address family. Both functions take an af argument, specifying the address family to be used in the conversion process. (Currently, only the AF_INET and AF_LINK address families are supported.)

The addr2ascii function is used to convert binary, network-format addresses into printable form. In addition to af, there are three other arguments. The addrp argument is a pointer to the network address to be converted. The len argument is the length of the address. The buf argument is an optional pointer to a caller-allocated buffer to hold the result; if a null pointer is passed, addr2ascii uses a statically-allocated buffer.

The ascii2addr function performs the inverse operation to addr2ascii. In addition to af, it takes two arguments, ascii and result. The ascii argument is a pointer to the string which is to be converted into binary. The result argument is a pointer to an appropriate network address structure for the specified family.

The following gives the appropriate structure to use for binary addresses in the specified family:

AF_INET
.Vt "struct in_addr" (in
.In arpa/inet.h )
AF_LINK
.Vt "struct sockaddr_dl" (in
.In net/if_dl.h )

AF_INET and AF_LINK constants are defined in
.In sys/socket.h .

RETURN VALUES

The addr2ascii function returns the address of the buffer it was passed, or a static buffer if the a null pointer was passed; on failure, it returns a null pointer. The ascii2addr function returns the length of the binary address in bytes, or -1 on failure.

EXAMPLES

The inet(3) functions inet_ntoa and inet_aton could be implemented thusly:
#include <sys/socket.h>
#include <arpa/inet.h>


char *
inet_ntoa(struct in_addr addr)
{
return addr2ascii(AF_INET, &addr, sizeof addr, 0);
}


int
inet_aton(const char *ascii, struct in_addr *addr)
{
return (ascii2addr(AF_INET, ascii, addr)
== sizeof(*addr));
}

In actuality, this cannot be done because addr2ascii and ascii2addr are implemented in terms of the inet(3) functions, rather than the other way around.

ERRORS

When a failure is returned, errno is set to one of the following values:
[ENAMETOOLONG]
The addr2ascii routine was passed a len argument which was inappropriate for the address family given by af.
[EPROTONOSUPPORT]
Either routine was passed an af argument other than AF_INET or AF_LINK.
[EINVAL]
The string passed to ascii2addr was improperly formatted for address family af.

SEE ALSO

inet(3), linkaddr(3), inet(4)

HISTORY

AUTHORS

BUGS


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