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Top Forums Shell Programming and Scripting Best performance to merge two files Post 303027340 by MadeInGermany on Thursday 13th of December 2018 04:31:09 PM
Old 12-13-2018
For this operation there is no faster way. Even "sed -i" would create a temporary new file.
If you want to do this operation multiple times, then there are ways for optimization.
For example
Code:
cat file1a file2 > file3; mv file3 file2
cat file1b file2 > file3; mv file3 file2

can be optimized
Code:
cat file1b file1a file2 > file3; mv file3 file2

 

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MERGE(1)						      General Commands Manual							  MERGE(1)

NAME
merge - three-way file merge SYNOPSIS
merge [ options ] file1 file2 file3 DESCRIPTION
merge incorporates all changes that lead from file2 to file3 into file1. The result ordinarily goes into file1. merge is useful for com- bining separate changes to an original. Suppose file2 is the original, and both file1 and file3 are modifications of file2. Then merge combines both changes. A conflict occurs if both file1 and file3 have changes in a common segment of lines. If a conflict is found, merge normally outputs a warning and brackets the conflict with and lines. A typical conflict will look like this: file A lines in file A ======= lines in file B file B If there are conflicts, the user should edit the result and delete one of the alternatives. OPTIONS
-A Output conflicts using the -A style of diff3(1), if supported by diff3. This merges all changes leading from file2 to file3 into file1, and generates the most verbose output. -E, -e These options specify conflict styles that generate less information than -A. See diff3(1) for details. The default is -E. With -e, merge does not warn about conflicts. -L label This option may be given up to three times, and specifies labels to be used in place of the corresponding file names in conflict reports. That is, merge -L x -L y -L z a b c generates output that looks like it came from files x, y and z instead of from files a, b and c. -p Send results to standard output instead of overwriting file1. -q Quiet; do not warn about conflicts. -V Print version number. DIAGNOSTICS
Exit status is 0 for no conflicts, 1 for some conflicts, 2 for trouble. IDENTIFICATION
Author: Walter F. Tichy. Manual Page Revision: ; Release Date: . Copyright (C) 1982, 1988, 1989 Walter F. Tichy. Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert. SEE ALSO
diff3(1), diff(1), rcsmerge(1), co(1). BUGS
It normally does not make sense to merge binary files as if they were text, but merge tries to do it anyway. GNU MERGE(1)
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