getprotoent(3) Library Functions Manual getprotoent(3)
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 data-
base (see protocols(5)) and returns a protoent structure containing the
broken-out fields from the entry. A connection is opened to the data-
base 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 en-
try from the database that matches the protocol number number. A con-
nection 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(), │ Thread safety │ MT-Unsafe race:protoent locale │
│ endprotoent() │ │ │
└────────────────────┴───────────────┴─────────────────────────────────┘
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 6.9.1 2024-05-02 getprotoent(3)
Generated by dwww version 1.16 on Tue Dec 16 05:01:38 CET 2025.