Very Computer

by **Amit** » Fri, 19 Oct 2001 15:10:43

I'm trying to write a little app which resolves a machine name. I'm using
the gethostbyname( ) function, and I've included the netdb.h file in my
program. But I'm not able to compile the program, the compiler says
"gethostbyname" undefined. Can anyone help? Thanks

by **Logan Sh** » Fri, 19 Oct 2001 15:18:26

>I'm trying to write a little app which resolves a machine name. I'm using
>the gethostbyname( ) function, and I've included the netdb.h file in my
>program. But I'm not able to compile the program, the compiler says
>"gethostbyname" undefined. Can anyone help? Thanks

gethostbyname() is defined in a library, but that library isn't one of
the ones that the linker uses by default. So, you'll have to tell the
linker to use that library using the "-lnsl" command line argument.

For example, if you're doing this:

gcc -o foo foo.c

you'd want to change it to this:

gcc -o foo foo.c -lnsl

Hope that helps.

- Logan
--
"In order to be prepared to hope in what does not deceive,
we must first lose hope in everything that deceives."

Georges Bernanos

by **Amit** » Fri, 19 Oct 2001 15:40:09

Thanks, Logan, it worked..
all I did was give the compiler the additional parameter and it worked.
Thanks!

> >I'm trying to write a little app which resolves a machine name. I'm using
> >the gethostbyname( ) function, and I've included the netdb.h file in my
> >program. But I'm not able to compile the program, the compiler says
> >"gethostbyname" undefined. Can anyone help? Thanks

> gethostbyname() is defined in a library, but that library isn't one of
> the ones that the linker uses by default. So, you'll have to tell the
> linker to use that library using the "-lnsl" command line argument.

> For example, if you're doing this:

> gcc -o foo foo.c

> you'd want to change it to this:

> gcc -o foo foo.c -lnsl

> Hope that helps.

> - Logan
> --
> "In order to be prepared to hope in what does not deceive,
> we must first lose hope in everything that deceives."

> Georges Bernanos

by **ultraspa..** » Fri, 19 Oct 2001 16:16:12

># gethostbyname() is defined in a library, but that library isn't one of
># the ones that the linker uses by default. So, you'll have to tell the
># linker to use that library using the "-lnsl" command line argument.
>#
># gcc -o foo foo.c -lnsl
>I wonder why the man pages show the necessary
>includes, but not the necessary libraries.

An excerpt from the gethostbyname man page:

NAME
gethostbyname, gethostbyname_r, gethostbyaddr,
gethostbyaddr_r, gethostent, gethostent_r, sethostent,
endhostent - get network host entry

SYNOPSIS
cc [ flag ... ] file ... -lnsl [ library ... ]
#include <netdb.h>

Doesn't the "-lnsl" indicate the necessary library?

by **Tony Walto** » Fri, 19 Oct 2001 17:57:39

> #
> # gethostbyname() is defined in a library, but that library isn't one of
> # the ones that the linker uses by default. So, you'll have to tell the
> # linker to use that library using the "-lnsl" command line argument.
> #
> # gcc -o foo foo.c -lnsl

> I wonder why the man pages show the necessary
> includes, but not the necessary libraries.

Whut?

NAME
gethostbyname, gethostbyname_r, gethostbyaddr,
gethostbyaddr_r, gethostent, gethostent_r, sethostent,
endhostent - get network host entry

SYNOPSIS
cc [ flag ... ] file ... -lnsl [ library ... ]
#include <netdb.h>

The bit that says "-lnsl" is sort of a Big Clue.

Try a couple more:

NAME
cos - cosine function

SYNOPSIS
cc [ flag ... ] file ... -lm [ library ... ]
#include <math.h>

OK, needs -lm

NAME
kstat_open, kstat_close - initialize kernel statistics
facility

SYNOPSIS
cc[ flag ... ] file ... -lkstat [ library ...]
#include <kstat.h>

Perhaps that one might need -lkstat

And so on.

--
Tony

by **Joerg Schilli** » Fri, 19 Oct 2001 20:00:27

>#
># gethostbyname() is defined in a library, but that library isn't one of
># the ones that the linker uses by default. So, you'll have to tell the
># linker to use that library using the "-lnsl" command line argument.
>#
># gcc -o foo foo.c -lnsl

>I wonder why the man pages show the necessary
>includes, but not the necessary libraries.

Sometimes it helps to read.....

Network Functions gethostbyname(3N)

NAME
gethostbyname, gethostbyname_r, gethostbyaddr,
gethostbyaddr_r, gethostent, gethostent_r, sethostent,
endhostent - get network host entry

SYNOPSIS
cc [ flag ... ] file ... -lnsl [ library ... ]

#include <netdb.h>

struct hostent *gethostbyname(const char *name);

struct hostent *gethostbyname_r(const char *name,
struct hostent *result, char *buffer, int buflen,
int *h_errnop);

Taken from S 7 !!! manuals (not S 9 ;-)

--

URL: http://www.fokus.gmd.de/usr/schilling ftp://ftp.fokus.gmd.de/pub/unix

Very Computer

network program compile problem

network program compile problem

network program compile problem

network program compile problem

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network program compile problem

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