Provided by: manpages-dev_6.7-2_all 
NAME
getprotoent, getprotobyname, getprotobynumber, setprotoent, endprotoent - get protocol entry
LIBRARY
Standard C library (libc, -lc)
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 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.
RETURN VALUE
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.
FILES
/etc/protocols
protocol database file
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌──────────────────────────────┬───────────────┬────────────────────────────────────────────────────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────┼───────────────┼────────────────────────────────────────────────────────┤
│ getprotoent() │ Thread safety │ MT-Unsafe race:protoent race:protoentbuf locale │
├──────────────────────────────┼───────────────┼────────────────────────────────────────────────────────┤
│ getprotobyname() │ Thread safety │ MT-Unsafe race:protobyname locale │
├──────────────────────────────┼───────────────┼────────────────────────────────────────────────────────┤
│ getprotobynumber() │ Thread safety │ MT-Unsafe race:protobynumber locale │
├──────────────────────────────┼───────────────┼────────────────────────────────────────────────────────┤
│ setprotoent(), endprotoent() │ Thread safety │ MT-Unsafe race:protoent locale │
└──────────────────────────────┴───────────────┴────────────────────────────────────────────────────────┘
In the above table, protoent in race:protoent signifies that if any of the functions setprotoent(),
getprotoent(), or endprotoent() are used in parallel in different threads of a program, then data races
could occur.
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001, 4.3BSD.
SEE ALSO
getnetent(3), getprotoent_r(3), getservent(3), protocols(5)
Linux man-pages 6.7 2023-10-31 getprotoent(3)