getprotobynumber(3)

1GETPROTOENT(3)             Linux Programmer's Manual            GETPROTOENT(3)
2
3
4

NAME

6       getprotoent, getprotobyname, getprotobynumber, setprotoent, endprotoent
7       - get protocol entry
8

SYNOPSIS

10       #include <netdb.h>
11
12       struct protoent *getprotoent(void);
13
14       struct protoent *getprotobyname(const char *name);
15       struct protoent *getprotobynumber(int proto);
16
17       void setprotoent(int stayopen);
18       void endprotoent(void);
19

DESCRIPTION

21       The getprotoent() function reads the  next  entry  from  the  protocols
22       database (see protocols(5)) and returns a protoent structure containing
23       the broken-out fields from the entry.  A connection is  opened  to  the
24       database if necessary.
25
26       The  getprotobyname() function returns a protoent structure for the en‐
27       try from the database that matches the protocol name name.   A  connec‐
28       tion is opened to the database if necessary.
29
30       The  getprotobynumber()  function  returns a protoent structure for the
31       entry from the database that matches the  protocol  number  number.   A
32       connection is opened to the database if necessary.
33
34       The setprotoent() function opens a connection to the database, and sets
35       the next entry to the first entry.  If stayopen is  nonzero,  then  the
36       connection  to  the database will not be closed between calls to one of
37       the getproto*() functions.
38
39       The endprotoent() function closes the connection to the database.
40
41       The protoent structure is defined in <netdb.h> as follows:
42
43           struct protoent {
44               char  *p_name;       /* official protocol name */
45               char **p_aliases;    /* alias list */
46               int    p_proto;      /* protocol number */
47           }
48
49       The members of the protoent structure are:
50
51       p_name The official name of the protocol.
52
53       p_aliases
54              A NULL-terminated list of alternative names for the protocol.
55
56       p_proto
57              The protocol number.
58

RETURN VALUE

60       The getprotoent(), getprotobyname(), and  getprotobynumber()  functions
61       return  a  pointer  to  a statically allocated protoent structure, or a
62       null pointer if an error occurs or the end of the file is reached.
63

FILES

65       /etc/protocols
66              protocol database file
67

ATTRIBUTES

69       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
70       tributes(7).
71
72       ┌───────────────────┬───────────────┬──────────────────────────────────┐
73       │Interface          │ Attribute     │ Value                            │
74       ├───────────────────┼───────────────┼──────────────────────────────────┤
75       │getprotoent()      │ Thread safety │ MT-Unsafe race:protoent          │
76       │                   │               │ race:protoentbuf locale          │
77       ├───────────────────┼───────────────┼──────────────────────────────────┤
78       │getprotobyname()   │ Thread safety │ MT-Unsafe race:protobyname       │
79       │                   │               │ locale                           │
80       ├───────────────────┼───────────────┼──────────────────────────────────┤
81       │getprotobynumber() │ Thread safety │ MT-Unsafe race:protobynumber     │
82       │                   │               │ locale                           │
83       ├───────────────────┼───────────────┼──────────────────────────────────┤
84       │setprotoent(),     │ Thread safety │ MT-Unsafe race:protoent locale   │
85       │endprotoent()      │               │                                  │
86       └───────────────────┴───────────────┴──────────────────────────────────┘
87       In  the above table, protoent in race:protoent signifies that if any of
88       the functions setprotoent(), getprotoent(), or endprotoent()  are  used
89       in  parallel  in  different threads of a program, then data races could
90       occur.
91

CONFORMING TO

93       POSIX.1-2001, POSIX.1-2008, 4.3BSD.
94

COLOPHON

99       This page is part of release 5.13 of the Linux  man-pages  project.   A
100       description  of  the project, information about reporting bugs, and the
101       latest    version    of    this    page,    can     be     found     at
102       https://www.kernel.org/doc/man-pages/.
103
104
105
106GNU                               2021-03-22                    GETPROTOENT(3)