| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON | The Linux Programming Interface |
GETPROTOENT_R(3) Linux Programmer's Manual GETPROTOENT_R(3)
getprotoent_r, getprotobyname_r, getprotobynumber_r - get protocol entry
(reentrant)
#include <netdb.h>
int getprotoent_r(struct protoent *result_buf, char *buf,
size_t buflen, struct protoent **result);
int getprotobyname_r(const char *name,
struct protoent *result_buf, char *buf,
size_t buflen, struct protoent **result);
int getprotobynumber_r(int proto,
struct protoent *result_buf, char *buf,
size_t buflen, struct protoent **result);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
getprotoent_r(), getprotobyname_r(), getprotobynumber_r():
_BSD_SOURCE || _SVID_SOURCE
The getprotoent_r(), getprotobyname_r(), and getprotobynumber_r() functions
are the reentrant equivalents of, respectively, getprotoent(3),
getprotobyname(3), and getprotobynumber(3). They differ in the way that the
protoent structure is returned, and in the function calling signature and
return value. This manual page describes just the differences from the
nonreentrant functions.
Instead of returning a pointer to a statically allocated protoent structure as
the function result, these functions copy the structure into the location
pointed to by result_buf.
The buf array is used to store the string fields pointed to by the returned
protoent structure. (The nonreentrant functions allocate these strings in
static storage.) The size of this array is specified in buflen. If buf is
too small, the call fails with the error ERANGE, and the caller must try again
with a larger buffer. (A buffer of length 1024 bytes should be sufficient for
most applications.)
If the function call successfully obtains a protocol record, then *result is
set pointing to result_buf; otherwise, *result is set to NULL.
On success, these functions return 0. On error, they return one of the
positive error numbers listed in ERRORS.
On error, record not found (getprotobyname_r(), getprotobynumber_r()), or end
of input (getprotoent_r()) result is set to NULL.
ENOENT (getprotoent_r()) No more records in database.
ERANGE buf is too small. Try again with a larger buffer (and increased
buflen).
These functions are GNU extensions. Functions with similar names exist on
some other systems, though typically with different calling signatures.
The program below uses getprotobyname_r() to retrieve the protocol record for
the protocol named in its first command-line argument. If a second (integer)
command-line argument is supplied, it is used as the initial value for buflen;
if getprotobyname_r() fails with the error ERANGE, the program retries with
larger buffer sizes. The following shell session shows a couple of sample
runs:
$ ./a.out tcp 1
ERANGE! Retrying with larger buffer
getprotobyname_r() returned: 0 (success) (buflen=78)
p_name=tcp; p_proto=6; aliases=TCP
$ ./a.out xxx 1
ERANGE! Retrying with larger buffer
getprotobyname_r() returned: 0 (success) (buflen=100)
Call failed/record not found
#define _GNU_SOURCE
#include <ctype.h>
#include <netdb.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#define MAX_BUF 10000
int
main(int argc, char *argv[])
{
int buflen, erange_cnt, s;
struct protoent result_buf;
struct protoent *result;
char buf[MAX_BUF];
char **p;
if (argc < 2) {
printf("Usage: %s proto-name [buflen]\n", argv[0]);
exit(EXIT_FAILURE);
}
buflen = 1024;
if (argc > 2)
buflen = atoi(argv[2]);
if (buflen > MAX_BUF) {
printf("Exceeded buffer limit (%d)\n", MAX_BUF);
exit(EXIT_FAILURE);
}
erange_cnt = 0;
do {
s = getprotobyname_r(argv[1], &result_buf,
buf, buflen, &result);
if (s == ERANGE) {
if (erange_cnt == 0)
printf("ERANGE! Retrying with larger buffer\n");
erange_cnt++;
/* Increment a byte at a time so we can see exactly
what size buffer was required */
buflen++;
if (buflen > MAX_BUF) {
printf("Exceeded buffer limit (%d)\n", MAX_BUF);
exit(EXIT_FAILURE);
}
}
} while (s == ERANGE);
printf("getprotobyname_r() returned: %s (buflen=%d)\n",
(s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" :
strerror(s), buflen);
if (s != 0 || result == NULL) {
printf("Call failed/record not found\n");
exit(EXIT_FAILURE);
}
printf("p_name=%s; p_proto=%d; aliases=",
result_buf.p_name, result_buf.p_proto);
for (p = result_buf.p_aliases; *p != NULL; p++)
printf("%s ", *p);
printf("\n");
exit(EXIT_SUCCESS);
}
getprotoent(3), protocols(5)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2010-09-10 GETPROTOENT_R(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface