GETPROTOENT(3)

NAME
getprotoent, getprotobynumber, getprotobyname, setprotoent, endprotoent - get protocol entry

LIBRARY
libc

SYNOPSIS
#include <netdb.h>
struct protoent *
getprotoent();
struct protoent *
getprotobyname(const char *name);
struct protoent *
getprotobynumber(int proto);
void
setprotoent(int stayopen);
void
endprotoent(void);

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 data base, /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 zero terminated list of alternative 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 net data base will not be closed after each call to getprotobyname() or getprotobynumber().

The endprotoent() function closes the file.

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

RETURN VALUES
Upon success, getprotoent(), getprotobyname(), and getprotobynumber() return a pointer to the protoent structure as described above. A NULL pointer is returned on EOF or error.

FILES
/etc/protocols

SEE ALSO
protocols(5)

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

BUGS
These 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.