+++ /dev/null
-'\" t
-.\" Copyright 2008, Linux Foundation, written by Michael Kerrisk
-.\" <mtk.manpages@gmail.com>
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.\"
-.TH getservent_r 3 (date) "Linux man-pages (unreleased)"
-.SH NAME
-getservent_r, getservbyname_r, getservbyport_r \- get
-service entry (reentrant)
-.SH LIBRARY
-Standard C library
-.RI ( libc ", " \-lc )
-.SH SYNOPSIS
-.nf
-.B #include <netdb.h>
-.P
-.BI "int getservent_r(struct servent *restrict " result_buf ,
-.BI " char " buf "[restrict ." buflen "], size_t " buflen ,
-.BI " struct servent **restrict " result );
-.BI "int getservbyname_r(const char *restrict " name ,
-.BI " const char *restrict " proto ,
-.BI " struct servent *restrict " result_buf ,
-.BI " char " buf "[restrict ." buflen "], size_t " buflen ,
-.BI " struct servent **restrict " result );
-.BI "int getservbyport_r(int " port ,
-.BI " const char *restrict " proto ,
-.BI " struct servent *restrict " result_buf ,
-.BI " char " buf "[restrict ." buflen "], size_t " buflen ,
-.BI " struct servent **restrict " result );
-.P
-.fi
-.RS -4
-Feature Test Macro Requirements for glibc (see
-.BR feature_test_macros (7)):
-.RE
-.P
-.BR getservent_r (),
-.BR getservbyname_r (),
-.BR getservbyport_r ():
-.nf
- Since glibc 2.19:
- _DEFAULT_SOURCE
- glibc 2.19 and earlier:
- _BSD_SOURCE || _SVID_SOURCE
-.fi
-.SH DESCRIPTION
-The
-.BR getservent_r (),
-.BR getservbyname_r (),
-and
-.BR getservbyport_r ()
-functions are the reentrant equivalents of, respectively,
-.BR getservent (3),
-.BR getservbyname (3),
-and
-.BR getservbyport (3).
-They differ in the way that the
-.I servent
-structure is returned,
-and in the function calling signature and return value.
-This manual page describes just the differences from
-the nonreentrant functions.
-.P
-Instead of returning a pointer to a statically allocated
-.I servent
-structure as the function result,
-these functions copy the structure into the location pointed to by
-.IR result_buf .
-.P
-The
-.I buf
-array is used to store the string fields pointed to by the returned
-.I servent
-structure.
-(The nonreentrant functions allocate these strings in static storage.)
-The size of this array is specified in
-.IR buflen .
-If
-.I buf
-is too small, the call fails with the error
-.BR ERANGE ,
-and the caller must try again with a larger buffer.
-(A buffer of length 1024 bytes should be sufficient for most applications.)
-.\" I can find no information on the required/recommended buffer size;
-.\" the nonreentrant functions use a 1024 byte buffer -- mtk.
-.P
-If the function call successfully obtains a service record, then
-.I *result
-is set pointing to
-.IR result_buf ;
-otherwise,
-.I *result
-is set to NULL.
-.SH RETURN VALUE
-On success, these functions return 0.
-On error, they return one of the positive error numbers listed in errors.
-.P
-On error, record not found
-.RB ( getservbyname_r (),
-.BR getservbyport_r ()),
-or end of input
-.RB ( getservent_r ())
-.I result
-is set to NULL.
-.SH ERRORS
-.TP
-.B ENOENT
-.RB ( getservent_r ())
-No more records in database.
-.TP
-.B ERANGE
-.I buf
-is too small.
-Try again with a larger buffer
-(and increased
-.IR buflen ).
-.SH ATTRIBUTES
-For an explanation of the terms used in this section, see
-.BR attributes (7).
-.TS
-allbox;
-lbx lb lb
-l l l.
-Interface Attribute Value
-T{
-.na
-.nh
-.BR getservent_r (),
-.BR getservbyname_r (),
-.BR getservbyport_r ()
-T} Thread safety MT-Safe locale
-.TE
-.SH VERSIONS
-Functions with similar names exist on some other systems,
-though typically with different calling signatures.
-.SH STANDARDS
-GNU.
-.SH EXAMPLES
-The program below uses
-.BR getservbyport_r ()
-to retrieve the service record for the port and protocol named
-in its first command-line argument.
-If a third (integer) command-line argument is supplied,
-it is used as the initial value for
-.IR buflen ;
-if
-.BR getservbyport_r ()
-fails with the error
-.BR ERANGE ,
-the program retries with larger buffer sizes.
-The following shell session shows a couple of sample runs:
-.P
-.in +4n
-.EX
-.RB "$" " ./a.out 7 tcp 1"
-ERANGE! Retrying with larger buffer
-getservbyport_r() returned: 0 (success) (buflen=87)
-s_name=echo; s_proto=tcp; s_port=7; aliases=
-.RB "$" " ./a.out 77777 tcp"
-getservbyport_r() returned: 0 (success) (buflen=1024)
-Call failed/record not found
-.EE
-.in
-.SS Program source
-\&
-.\" SRC BEGIN (getservent_r.c)
-.EX
-#define _GNU_SOURCE
-#include <ctype.h>
-#include <errno.h>
-#include <netdb.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-\&
-#define MAX_BUF 10000
-\&
-int
-main(int argc, char *argv[])
-{
- int buflen, erange_cnt, port, s;
- struct servent result_buf;
- struct servent *result;
- char buf[MAX_BUF];
- char *protop;
-\&
- if (argc < 3) {
- printf("Usage: %s port\-num proto\-name [buflen]\en", argv[0]);
- exit(EXIT_FAILURE);
- }
-\&
- port = htons(atoi(argv[1]));
- protop = (strcmp(argv[2], "null") == 0 ||
- strcmp(argv[2], "NULL") == 0) ? NULL : argv[2];
-\&
- buflen = 1024;
- if (argc > 3)
- buflen = atoi(argv[3]);
-\&
- if (buflen > MAX_BUF) {
- printf("Exceeded buffer limit (%d)\en", MAX_BUF);
- exit(EXIT_FAILURE);
- }
-\&
- erange_cnt = 0;
- do {
- s = getservbyport_r(port, protop, &result_buf,
- buf, buflen, &result);
- if (s == ERANGE) {
- if (erange_cnt == 0)
- printf("ERANGE! Retrying with larger buffer\en");
- 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)\en", MAX_BUF);
- exit(EXIT_FAILURE);
- }
- }
- } while (s == ERANGE);
-\&
- printf("getservbyport_r() returned: %s (buflen=%d)\en",
- (s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" :
- strerror(s), buflen);
-\&
- if (s != 0 || result == NULL) {
- printf("Call failed/record not found\en");
- exit(EXIT_FAILURE);
- }
-\&
- printf("s_name=%s; s_proto=%s; s_port=%d; aliases=",
- result_buf.s_name, result_buf.s_proto,
- ntohs(result_buf.s_port));
- for (char **p = result_buf.s_aliases; *p != NULL; p++)
- printf("%s ", *p);
- printf("\en");
-\&
- exit(EXIT_SUCCESS);
-}
-.EE
-.\" SRC END
-.SH SEE ALSO
-.BR getservent (3),
-.BR services (5)
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