Get protocol entry.

#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(), 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 include:

p_name

The official name of the protocol.

p_aliases

A zero terminated list of alternate names for the protocol.<</dd>

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.

Files

/etc/protocols

Bugs

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.

Return Values

Null pointer (0) returned on EOF or error.

Requirements