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1 | .\" Copyright (c) 1990, 1993 |
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32 | .\" @(#)recno.3 8.5 (Berkeley) 8/18/94 | |
33 | .\" | |
df21098d | 34 | .TH RECNO 3 2012-04-23 "" "Linux Programmer's Manual" |
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35 | .UC 7 |
36 | .SH NAME | |
37 | recno \- record number database access method | |
38 | .SH SYNOPSIS | |
39 | .nf | |
40 | .ft B | |
41 | #include <sys/types.h> | |
42 | #include <db.h> | |
43 | .ft R | |
44 | .fi | |
45 | .SH DESCRIPTION | |
df21098d MK |
46 | .IR "Note well" : |
47 | This page documents interfaces provided in glibc up until version 2.1. | |
48 | Since version 2.2, glibc no longer provides these interfaces. | |
49 | Probably, you are looking for the APIs provided by the | |
50 | .I libdb | |
51 | library instead. | |
52 | ||
fea681da | 53 | The routine |
1c9d4f95 | 54 | .BR dbopen (3) |
fea681da MK |
55 | is the library interface to database files. |
56 | One of the supported file formats is record number files. | |
57 | The general description of the database access methods is in | |
31e9a9ec | 58 | .BR dbopen (3), |
fea681da MK |
59 | this manual page describes only the recno specific information. |
60 | .PP | |
61 | The record number data structure is either variable or fixed-length | |
62 | records stored in a flat-file format, accessed by the logical record | |
63 | number. | |
64 | The existence of record number five implies the existence of records | |
65 | one through four, and the deletion of record number one causes | |
66 | record number five to be renumbered to record number four, as well | |
67 | as the cursor, if positioned after record number one, to shift down | |
68 | one record. | |
69 | .PP | |
70 | The recno access method specific data structure provided to | |
1c9d4f95 | 71 | .BR dbopen (3) |
a9a13a50 MK |
72 | is defined in the |
73 | .I <db.h> | |
74 | include file as follows: | |
fea681da | 75 | .PP |
088a639b | 76 | .in +4n |
b9f02710 | 77 | .nf |
fea681da | 78 | typedef struct { |
c09cb5f4 | 79 | unsigned long flags; |
aeb4b1fc MK |
80 | unsigned int cachesize; |
81 | unsigned int psize; | |
82 | int lorder; | |
83 | size_t reclen; | |
10ff70c5 | 84 | unsigned char bval; |
aeb4b1fc | 85 | char *bfname; |
fea681da | 86 | } RECNOINFO; |
b9f02710 | 87 | .fi |
ec5a588f | 88 | .in |
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89 | .PP |
90 | The elements of this structure are defined as follows: | |
91 | .TP | |
92 | flags | |
cebca1bd | 93 | The flag value is specified by ORing |
fea681da MK |
94 | any of the following values: |
95 | .RS | |
96 | .TP | |
4bd8c614 | 97 | .B R_FIXEDLEN |
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98 | The records are fixed-length, not byte delimited. |
99 | The structure element | |
100 | .I reclen | |
101 | specifies the length of the record, and the structure element | |
102 | .I bval | |
103 | is used as the pad character. | |
104 | Any records, inserted into the database, that are less than | |
105 | .I reclen | |
106 | bytes long are automatically padded. | |
107 | .TP | |
4bd8c614 | 108 | .B R_NOKEY |
fea681da | 109 | In the interface specified by |
1c9d4f95 | 110 | .BR dbopen (3), |
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111 | the sequential record retrieval fills in both the caller's key and |
112 | data structures. | |
4bd8c614 MK |
113 | If the |
114 | .B R_NOKEY | |
115 | flag is specified, the | |
fea681da MK |
116 | .I cursor |
117 | routines are not required to fill in the key structure. | |
118 | This permits applications to retrieve records at the end of files without | |
119 | reading all of the intervening records. | |
120 | .TP | |
4bd8c614 | 121 | .B R_SNAPSHOT |
fea681da | 122 | This flag requires that a snapshot of the file be taken when |
1c9d4f95 | 123 | .BR dbopen (3) |
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124 | is called, instead of permitting any unmodified records to be read from |
125 | the original file. | |
126 | .RE | |
127 | .TP | |
ec5a588f | 128 | .I cachesize |
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129 | A suggested maximum size, in bytes, of the memory cache. |
130 | This value is | |
131 | .B only | |
132 | advisory, and the access method will allocate more memory rather than fail. | |
133 | If | |
134 | .I cachesize | |
135 | is 0 (no size is specified) a default cache is used. | |
136 | .TP | |
ec5a588f | 137 | .I psize |
fea681da MK |
138 | The recno access method stores the in-memory copies of its records |
139 | in a btree. | |
140 | This value is the size (in bytes) of the pages used for nodes in that tree. | |
141 | If | |
142 | .I psize | |
143 | is 0 (no page size is specified) a page size is chosen based on the | |
144 | underlying file system I/O block size. | |
145 | See | |
31e9a9ec | 146 | .BR btree (3) |
fea681da MK |
147 | for more information. |
148 | .TP | |
ec5a588f | 149 | .I lorder |
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150 | The byte order for integers in the stored database metadata. |
151 | The number should represent the order as an integer; for example, | |
152 | big endian order would be the number 4,321. | |
153 | If | |
154 | .I lorder | |
155 | is 0 (no order is specified) the current host order is used. | |
156 | .TP | |
ec5a588f | 157 | .I reclen |
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158 | The length of a fixed-length record. |
159 | .TP | |
ec5a588f | 160 | .I bval |
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161 | The delimiting byte to be used to mark the end of a record for |
162 | variable-length records, and the pad character for fixed-length | |
163 | records. | |
9f8e673e | 164 | If no value is specified, newlines ("\\n") are used to mark the end |
fea681da MK |
165 | of variable-length records and fixed-length records are padded with |
166 | spaces. | |
167 | .TP | |
ec5a588f | 168 | .I bfname |
fea681da MK |
169 | The recno access method stores the in-memory copies of its records |
170 | in a btree. | |
ec5a588f MK |
171 | If |
172 | .I bfname | |
173 | is non-NULL, it specifies the name of the btree file, | |
1c9d4f95 MK |
174 | as if specified as the filename for a |
175 | .BR dbopen (3) | |
176 | of a btree file. | |
fea681da | 177 | .PP |
ec5a588f MK |
178 | The data part of the key/data pair used by the |
179 | .I recno | |
180 | access method | |
fea681da MK |
181 | is the same as other access methods. |
182 | The key is different. | |
183 | The | |
184 | .I data | |
185 | field of the key should be a pointer to a memory location of type | |
186 | .IR recno_t , | |
a9a13a50 | 187 | as defined in th |
ec5a588f | 188 | .I <db.h> |
a9a13a50 | 189 | include file. |
fea681da MK |
190 | This type is normally the largest unsigned integral type available to |
191 | the implementation. | |
192 | The | |
193 | .I size | |
194 | field of the key should be the size of that type. | |
195 | .PP | |
466dbc8b | 196 | Because there can be no metadata associated with the underlying |
fea681da | 197 | recno access method files, any changes made to the default values |
75b94dc3 | 198 | (e.g., fixed record length or byte separator value) must be explicitly |
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199 | specified each time the file is opened. |
200 | .PP | |
201 | In the interface specified by | |
1c9d4f95 | 202 | .BR dbopen (3), |
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203 | using the |
204 | .I put | |
205 | interface to create a new record will cause the creation of multiple, | |
206 | empty records if the record number is more than one greater than the | |
207 | largest record currently in the database. | |
208 | .SH ERRORS | |
209 | The | |
210 | .I recno | |
211 | access method routines may fail and set | |
212 | .I errno | |
213 | for any of the errors specified for the library routine | |
31e9a9ec | 214 | .BR dbopen (3) |
fea681da MK |
215 | or the following: |
216 | .TP | |
747944fe | 217 | .B EINVAL |
fea681da MK |
218 | An attempt was made to add a record to a fixed-length database that |
219 | was too large to fit. | |
e37e3282 MK |
220 | .SH BUGS |
221 | Only big and little endian byte order is supported. | |
fea681da | 222 | .SH "SEE ALSO" |
ac5e6a36 | 223 | .BR btree (3), |
31e9a9ec MK |
224 | .BR dbopen (3), |
225 | .BR hash (3), | |
d8aaa1d3 | 226 | .BR mpool (3) |
173fe7e7 | 227 | |
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228 | .IR "Document Processing in a Relational Database System" , |
229 | Michael Stonebraker, Heidi Stettner, Joseph Kalash, Antonin Guttman, | |
230 | Nadene Lynn, Memorandum No. UCB/ERL M82/32, May 1982. |