struct protoent *getprotobyname(const char *name);
struct protoent *getprotobynumber(int proto);
struct protoent *getprotoent(void);
void setprotoent(int stayopen);
These functions shall retrieve information about protocols. This information is considered to be stored in a database that can be accessed sequentially or randomly. The implementation of this database is unspecified.
The setprotoent() function shall open a connection to the database, and set the next entry to the first entry. If the stayopen argument is non-zero, the connection to the network protocol database shall not be closed after each call to getprotoent() (either directly, or indirectly through one of the other getproto*() functions), and the implementation may maintain an open file descriptor for the database.
The getprotobyname() function shall search the database from the beginning and find the first entry for which the protocol name specified by name matches the p_name member, opening and closing a connection to the database as necessary.
The getprotobynumber() function shall search the database from the beginning and find the first entry for which the protocol number specified by proto matches the p_proto member, opening and closing a connection to the database as necessary.
The getprotoent() function shall read the next entry of the database, opening and closing a connection to the database as necessary.
The getprotobyname(), getprotobynumber(), and getprotoent() functions shall each return a pointer to a protoent structure, the members of which shall contain the fields of an entry in the network protocol database.
The endprotoent() function shall close the connection to the database, releasing any open file descriptor.
These functions need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.
Upon successful completion, getprotobyname(), getprotobynumber(), and getprotoent() return a pointer to a protoent structure if the requested entry was found, and a null pointer if the end of the database was reached or the requested entry was not found. Otherwise, a null pointer is returned.
No errors are defined.
The following sections are informative.
The getprotobyname(), getprotobynumber(), and getprotoent() functions may return pointers to static data, which may be overwritten by subsequent calls to any of these functions.
The Base Definitions volume of IEEE Std 1003.1-2001, <netdb.h>