man3/getnetent_r.3

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  26 .TH GETNETENT_R 3  2017-09-15 "GNU" "Linux Programmer's Manual"
  27 .SH NAME
  28 getnetent_r, getnetbyname_r, getnetbyaddr_r \- get
  29 network entry (reentrant)
  30 .SH SYNOPSIS
  31 .nf
  32 .B #include <netdb.h>
  33 .PP
  34 .BI "int getnetent_r(struct netent *" result_buf ", char *" buf ,
  35 .BI "                size_t " buflen ", struct netent **" result ,
  36 .BI "                int *" h_errnop );
  37 .PP
  38 .BI "int getnetbyname_r(const char *" name ,
  39 .BI "                struct netent *" result_buf ", char *" buf ,
  40 .BI "                size_t " buflen ", struct netent **" result ,
  41 .BI "                int *" h_errnop );
  42 .PP
  43 .BI "int getnetbyaddr_r(uint32_t " net ", int " type ,
  44 .BI "                struct netent *" result_buf ", char *" buf ,
  45 .BI "                size_t " buflen ", struct netent **" result ,
  46 .BI "                int *" h_errnop );
  47 .PP
  48 .fi
  49 .in -4n
  50 Feature Test Macro Requirements for glibc (see
  51 .BR feature_test_macros (7)):
  52 .ad l
  53 .in
  54 .PP
  55 .BR getnetent_r (),
  56 .BR getnetbyname_r (),
  57 .BR getnetbyaddr_r ():
  58     Since glibc 2.19:
  59         _DEFAULT_SOURCE
  60     Glibc 2.19 and earlier:
  61         _BSD_SOURCE || _SVID_SOURCE
  62 .ad b
  63 .SH DESCRIPTION
  64 The
  65 .BR getnetent_r (),
  66 .BR getnetbyname_r (),
  67 and
  68 .BR getnetbyaddr_r ()
  69 functions are the reentrant equivalents of, respectively,
  70 .BR getnetent (3),
  71 .BR getnetbyname (3),
  72 and
  73 .BR getnetbynumber (3).
  74 They differ in the way that the
  75 .I netent
  76 structure is returned,
  77 and in the function calling signature and return value.
  78 This manual page describes just the differences from
  79 the nonreentrant functions.
  80 .PP
  81 Instead of returning a pointer to a statically allocated
  82 .I netent
  83 structure as the function result,
  84 these functions copy the structure into the location pointed to by
  85 .IR result_buf .
  86 .PP
  87 The
  88 .I buf
  89 array is used to store the string fields pointed to by the returned
  90 .I netent
  91 structure.
  92 (The nonreentrant functions allocate these strings in static storage.)
  93 The size of this array is specified in
  94 .IR buflen .
  95 If
  96 .I buf
  97 is too small, the call fails with the error
  98 .BR ERANGE ,
  99 and the caller must try again with a larger buffer.
 100 (A buffer of length 1024 bytes should be sufficient for most applications.)
 101 .\" I can find no information on the required/recommended buffer size;
 102 .\" the nonreentrant functions use a 1024 byte buffer -- mtk.
 103 .PP
 104 If the function call successfully obtains a network record, then
 105 .I *result
 106 is set pointing to
 107 .IR result_buf ;
 108 otherwise,
 109 .I *result
 110 is set to NULL.
 111 .PP
 112 The buffer pointed to by
 113 .I h_errnop
 114 is used to return the value that would be stored in the global variable
 115 .I h_errno
 116 by the nonreentrant versions of these functions.
 117 .\" getnetent.3 doesn't document any use of h_errno, but nevertheless
 118 .\" the nonreentrant functions no seem to set h_errno.
 119 .SH RETURN VALUE
 120 On success, these functions return 0.
 121 On error, they return one of the positive error numbers listed in ERRORS.
 122 .PP
 123 On error, record not found
 124 .RB ( getnetbyname_r (),
 125 .BR getnetbyaddr_r ()),
 126 or end of input
 127 .RB ( getnetent_r ())
 128 .I result
 129 is set to NULL.
 130 .SH ERRORS
 131 .TP
 132 .B ENOENT
 133 .RB ( getnetent_r ())
 134 No more records in database.
 135 .TP
 136 .B ERANGE
 137 .I buf
 138 is too small.
 139 Try again with a larger buffer
 140 (and increased
 141 .IR buflen ).
 142 .SH ATTRIBUTES
 143 For an explanation of the terms used in this section, see
 144 .BR attributes (7).
 145 .ad l
 146 .TS
 147 allbox;
 148 lbw17 lb lb
 149 l l l.
 150 Interface       Attribute       Value
 151 T{
 152 .BR getnetent_r (),
 153 .BR getnetbyname_r (),
 154 .BR getnetbyaddr_r ()
 155 T}      Thread safety   MT-Safe locale
 156 .TE
 157 .ad
 158 .SH CONFORMING TO
 159 These functions are GNU extensions.
 160 Functions with similar names exist on some other systems,
 161 though typically with different calling signatures.
 162 .SH SEE ALSO
 163 .BR getnetent (3),
 164 .BR networks (5)