getprotoent(3) - Linux man page

Name

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

Synopsis

#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);

Description

The getprotoent() function reads the next line from the file /etc/protocols and returns a structure protoent containing the broken out fields from the line. The /etc/protocols file is opened if necessary.

The getprotobyname() function returns a protoent structure for the line from /etc/protocols that matches the protocol name name.

The getprotobynumber() function returns a protoent structure for the line that matches the protocol number number.

The setprotoent() function opens and rewinds the /etc/protocols file. If stayopen is true (1), then the file will not be closed between calls to getprotobyname() or getprotobynumber().

The endprotoent() function closes /etc/protocols.

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 zero terminated list of alternative names for the protocol.
p_proto: The protocol number.

Return Value

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

Files

/etc/protocols

protocol database file

Conforming To

4.3BSD, POSIX.1-2001.

Referenced By

endservent(3), getsockopt(2), nsswitch.conf(5), socket(2)