format.so

berkeley db 4.6.21的源码。berkeley db是一个简单的数据库管理系统

m4_comment([$Id: format.so,v 10.16 2001/03/13 20:39:47 bostic Exp $])

m4_ref_title(Dumping and Reloading,
    Dump output formats,, dumpload/utility, dumpload/text)

m4_p([dnl
There are two output formats used by m4_ref(db_dump) and m4_ref(db_dump185).])

m4_p([dnl
In both output formats, the first few lines of the output contain header
information describing the underlying access method, filesystem page size,
and other bookkeeping information.])

m4_p([dnl
The header information starts with a single line, VERSION=N, where N is
the version number of the dump output format.])

m4_p([dnl
The header information is then output in name=value pairs, where name may
be any of the keywords listed in the m4_ref(db_load) manual page, and
value will be its value.  Although this header information can be manually
edited before the database is reloaded, there is rarely any reason to do
so because all of this information can also be specified or overridden by
command-line arguments to m4_ref(db_load).])

m4_p([dnl
The header information ends with single line HEADER=END.])

m4_p([dnl
Following the header information are the key/data pairs from the
database.  If the database being dumped is a Btree or Hash database, or
if the m4_bold(-k) option was specified, the output will be paired lines
of text where the first line of the pair is the key item, and the second
line of the pair is its corresponding data item.  If the database being
dumped is a Queue or Recno database, and the m4_bold(-k) option was not
specified, the output will be lines of text where each line is the next
data item for the database.  Each of these lines is preceded by a single
space.])

m4_p([dnl
If the m4_option(p) option to m4_ref(db_dump) or m4_ref(db_dump185) was
specified, the key/data lines will consist of single characters
representing any characters from the database that are m4_italic([printing
characters]) and backslash (m4_bold(m4_backslash([]))) escaped characters
for any that were not.  Backslash characters appearing in the output mean
one of two things: if the backslash character precedes another backslash
character, it means that a literal backslash character occurred in the
key or data item.  If the backslash character precedes any other
character, the next two characters must be interpreted as hexadecimal
specification of a single character; for example, m4_bold([m4_backslash()0a])
is a newline character in the ASCII character set.])

m4_p([dnl
Although some care should be exercised, it is perfectly reasonable to use
standard text editors and tools to edit databases dumped using the
m4_option(p) option before reloading them using the m4_ref(db_load)
utility.])

m4_p([dnl
Note that the definition of a printing character may vary from system to
system, so database representations created using the m4_option(p)
option may be less portable than those created without it.])

m4_p([dnl
If the m4_option(p) option to m4_ref(db_dump) or m4_ref(db_dump185) is
not specified, each output line will consist of paired hexadecimal values;
for example, the line m4_bold(726f6f74) is the string m4_bold(root) in
the ASCII character set.])

m4_p([dnl
In all output formats, the key and data items are ended by a single line
DATA=END.])

m4_p([dnl
Where multiple databases have been dumped from a file, the overall output
will repeat; that is, a new set of headers and a new set of data items.])

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