GETPROTOENT_R

NAME

SYNOPSIS

#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);

getprotoent_r(), getprotobyname_r(), getprotobynumber_r(): _BSD_SOURCE || _SVID_SOURCE  

DESCRIPTION

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 non-reentrant 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.  

RETURN VALUE

On error, record not found (getprotobyname_r(), getprotobynumber_r()), or end of input (getprotoent_r()) result is set to NULL.  

ERRORS

ENOENT

(getprotoent_r()) No more records in database.

ERANGE

buf is too small. Try again with a larger buffer (and increased buflen).

CONFORMING TO

EXAMPLE

$ ./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

Program source

#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);
}

SEE ALSO

COLOPHON