getprotobynumber (3)

#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 getprotoent() function reads the next entry from the protocols database (see protocols(5)) and returns a protoent structure containing the broken-out fields from the entry. A connection is opened to the database if necessary.

The getprotobyname() function returns a protoent structure for the entry from the database that matches the protocol name name. A connection is opened to the database if necessary.

The getprotobynumber() function returns a protoent structure for the entry from the database that matches the protocol number number. A connection is opened to the database if necessary.

The setprotoent() function opens a connection to the database, and sets the next entry to the first entry. If stayopen is nonzero, then the connection to the database will not be closed between calls to one of the getproto*() functions.

The endprotoent() function closes the connection to the database.

The protoent structure is defined in <netdb.h> as follows:

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

The members of the protoent structure are:

p_name

The official name of the protocol.

p_aliases

A NULL-terminated list of alternative names for the protocol.

p_proto

The protocol number.

The getprotoent(), getprotobyname() and getprotobynumber() functions return a pointer to a statically allocated protoent structure, or a null pointer if an error occurs or the end of the file is reached.

/etc/protocols

protocol database file

4.3BSD, POSIX.1-2001.

getnetent(3), getprotoent_r(3), getservent(3), protocols(5)

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