GETPROTOENT(3)

NAME
getprotoent, getprotoent_r, getprotobynumber, getprotobynumber_r, getprotobyname, getprotobyname_r, setprotoent, setprotoent_r, endprotoent, endprotoent_r - get protocol entry

SYNOPSIS
#include <netdb.h>
struct protoent *
getprotoent(void);
int
getprotoent_r(struct protoent *protoent, struct protoent_data *protoent_data);
struct protoent *
getprotobyname(const char *name);
int
getprotobyname_r(const char *name, struct protoent *protoent, struct protoent_data *protoent_data);
struct protoent *
getprotobynumber(int proto);
int
getprotobynumber_r(int proto, struct protoent *protoent, struct protoent_data *protoent_data);
void
setprotoent(int stayopen);
void
setprotoent_r(int stayopen, struct protoent_data *protoent_data);
void
endprotoent(void);
void
endprotoent_r(struct protoent_data *protoent_data);

DESCRIPTION
The getprotoent(), getprotobyname(), and getprotobynumber() functions each return a pointer to an object with the following structure containing the broken-out fields of a line in the network protocol database, /etc/protocols.

    struct	protoent {
    	char	*p_name;	/* official name of protocol */
    	char	**p_aliases;	/* alias list */
    	int	p_proto;	/* protocol number */
    };

The members of this structure are:

p_name
    The official name of the protocol.

p_aliases
    A null-terminated list of alternate names for the protocol.

p_proto
    The protocol number.

The getprotoent() function reads the next line of the file, opening the file if necessary.

The setprotoent() function opens and rewinds the file. If the stayopen flag is non-zero, the protocol database will not be closed after each call to getprotobyname() or getprotobynumber().

The endprotoent() function closes the file.

The getprotobyname() and getprotobynumber() functions sequentially search from the beginning of the file until a matching protocol name or protocol number is found, or until EOF is encountered.

The getprotoent_r(), getprotobyport_r(), getprotobyname_r(), setprotoent_r(), and endprotoent_r() functions are reentrant versions of the above functions that take a pointer to a protoent_data structure which is used to store state information. The structure must be zero-filled before it is used and should be considered opaque for the sake of portability.

The getprotoent_r(), getprotobyport_r(), and getprotobyname_r() functions also take a pointer to a protoent structure which is used to store the results of the database lookup.

RETURN VALUES
The getprotoent(), getprotobyport(), and getprotobyname() functions return a pointer to a protoent structure on success or a null pointer if end-of-file is reached or an error occurs.

The getprotoent_r(), getprotobyport_r(), and getprotobyname_r() functions return 0 on success or -1 if end-of-file is reached or an error occurs.

FILES
/etc/protocols

SEE ALSO
protocols(5)

STANDARDS
The getprotoent(), getprotobynumber(), getprotobyname(), setprotoent(), and endprotoent() functions conform to p1003.1-2004.

The getprotoent_r(), getprotobyport_r(), getprotobyname_r(), setprotoent_r(), and endprotoent_r() functions are not currently standardized. This implementation follows the API used by HP, IBM, and Digital.

HISTORY
The getprotoent(), getprotobynumber(), getprotobyname(), setprotoent(), and endprotoent() functions appeared in 4.2BSD.

The getprotoent_r(), getprotobyport_r(), getprotobyname_r(), setprotoent_r(), and endprotoent_r() functions appeared in OpenBSD 3.7.

BUGS
The non-reentrant functions use a static data space; if the data is needed for future use, it should be copied before any subsequent calls overwrite it. Only the Internet protocols are currently understood.