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GETPROTOENT_R(3) | Linux Programmer's Manual | GETPROTOENT_R(3) |
NAME¶
getprotoent_r, getprotobyname_r, getprotobynumber_r - get protocol entry (reentrant)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);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_BSD_SOURCE || _SVID_SOURCE
DESCRIPTION¶
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.RETURN VALUE¶
On success, these functions return 0. On error, they return one of the positive error numbers listed in ERRORS.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¶
These functions are GNU extensions. Functions with similar names exist on some other systems, though typically with different calling signatures.EXAMPLE¶
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
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¶
getprotoent(3), protocols(5)COLOPHON¶
This page is part of release 3.44 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/.2010-09-10 | GNU |