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GETPROTOENT(3) Library Functions Manual GETPROTOENT(3)

getprotoent, getprotobynumber, getprotobyname, setprotoent, endprotoentget protocol entry

library “libc”

#include <netdb.h>

struct protoent *
getprotoent(void);

struct protoent *
getprotobyname(const char *name);

struct protoent *
getprotobynumber(int proto);

void
setprotoent(int stayopen);

void
endprotoent(void);

The (), 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 alternate names for the protocol.
p_proto
The protocol number.

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

The () 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 () function closes the file.

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

Null pointer returned on EOF or error.

/etc/protocols
 

protocols(5)

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

These functions use a thread-specific 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.

June 4, 1993 FreeBSD-12.0