1DBMERGE(1)            User Contributed Perl Documentation           DBMERGE(1)
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NAME

6       dbmerge - merge all inputs in sorted order based on the the specified
7       columns
8

SYNOPSIS

10           dbmerge --input A.fsdb --input B.fsdb [-T TemporaryDirectory] [-nNrR] column [column...]
11
12       or
13           cat A.fsdb | dbmerge --input - --input B.fsdb [-T
14       TemporaryDirectory] [-nNrR] column [column...]
15
16       or
17           dbmerge [-T TemporaryDirectory] [-nNrR] column [column...] --inputs
18       A.fsdb [B.fsdb ...]
19
20       or
21           { echo "A.fsdb"; echo "B.fsdb" } | dbmerge --xargs column
22       [column...]
23

DESCRIPTION

25       Merge all provided, pre-sorted input files, producing one sorted
26       result.  Inputs can both be specified with "--input", or with
27       "--inputs", or one can come from standard input and the other from
28       "--input".  With "--xargs", each line of standard input is a filename
29       for input.
30
31       Inputs must have identical schemas (columns, column order, and field
32       separators).
33
34       Unlike dbmerge2, dbmerge supports an arbitrary number of input files.
35
36       Because this program is intended to merge multiple sources, it does not
37       default to reading from standard input.  If you wish to read standard
38       input, giv - as an explicit input source.
39
40       Also, because we deal with multiple input files, this module doesn't
41       output anything until it's run.
42
43       dbmerge consumes a fixed amount of memory regardless of input size.  It
44       therefore buffers output on disk as necessary.  (Merging is implemented
45       a series of two-way merges and possibly an n-way merge at the end, so
46       disk space is O(number of records).)
47
48       dbmerge will merge data in parallel, if possible.  The "--parallelism"
49       option can control the degree of parallelism, if desired.
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OPTIONS

52       General option:
53
54       --xargs
55           Expect that input filenames are given, one-per-line, on standard
56           input.  (In this case, merging can start incrementally.)
57
58       --removeinputs
59           Delete the source files after they have been consumed.  (Defaults
60           off, leaving the inputs in place.)
61
62       -T TmpDir
63           where to put tmp files.  Also uses environment variable TMPDIR, if
64           -T is not specified.  Default is /tmp.
65
66       --parallelism N or -j N
67           Allow up to N merges to happen in parallel.  Default is the number
68           of CPUs in the machine.
69
70       --endgame (or --noendgame)
71           Enable endgame mode, extra parallelism when finishing up.  (On by
72           default.)
73
74       Sort specification options (can be interspersed with column names):
75
76       -r or --descending
77           sort in reverse order (high to low)
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79       -R or --ascending
80           sort in normal order (low to high)
81
82       -n or --numeric
83           sort numerically
84
85       -N or --lexical
86           sort lexicographically
87
88       This module also supports the standard fsdb options:
89
90       -d  Enable debugging output.
91
92       -i or --input InputSource
93           Read from InputSource, typically a file name, or "-" for standard
94           input, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue
95           objects.
96
97       -o or --output OutputDestination
98           Write to OutputDestination, typically a file name, or "-" for
99           standard output, or (if in Perl) a IO::Handle, Fsdb::IO or
100           Fsdb::BoundedQueue objects.
101
102       --autorun or --noautorun
103           By default, programs process automatically, but Fsdb::Filter
104           objects in Perl do not run until you invoke the run() method.  The
105           "--(no)autorun" option controls that behavior within Perl.
106
107       --header H
108           Use H as the full Fsdb header, rather than reading a header from
109           then input.
110
111       --help
112           Show help.
113
114       --man
115           Show full manual.
116

SAMPLE USAGE

118   Input:
119       File a.fsdb:
120
121           #fsdb cid cname
122           11 numanal
123           10 pascal
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125       File b.fsdb:
126
127           #fsdb cid cname
128           12 os
129           13 statistics
130
131       These two files are both sorted by "cname", and they have identical
132       schemas.
133
134   Command:
135           dbmerge --input a.fsdb --input b.fsdb cname
136
137       or
138
139           cat a.fsdb | dbmerge --input b.fsdb cname
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141   Output:
142           #fsdb      cid     cname
143           11 numanal
144           12 os
145           10 pascal
146           13 statistics
147           #  | dbmerge --input a.fsdb --input b.fsdb cname
148

SEE ALSO

150       dbmerge2(1), dbsort(1), Fsdb(3)
151

153       Copyright (C) 1991-2020 by John Heidemann <johnh@isi.edu>
154
155       This program is distributed under terms of the GNU general public
156       license, version 2.  See the file COPYING with the distribution for
157       details.
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161perl v5.38.0                      2023-07-20                        DBMERGE(1)
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