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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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diff3(1)						      General Commands Manual							  diff3(1)

NAME
diff3 - 3-way differential file comparison SYNOPSIS
file1 file2 file3 DESCRIPTION
compares three versions of a file, and prints disagreeing ranges of text flagged with these codes: all three files differ file1 is different file2 is different file3 is different The type of change required to convert a given range of a given file to some other is indicated in one of these ways: Text is to be appended after line number n1 in file f, where f = or Text is to be changed in the range line n1 through line n2. If n1 = n2, the range can be abbreviated to n1. The original contents of the range follows immediately after a indication. When the contents of two files are identical, the contents of the lower-numbered file is suppressed. Produces a script for the editor that can be used to incorporate into file1 all changes between file2 and file3 (see ed(1)); i.e., the changes that normally would be flagged and Produces a script to incorporate only changes flagged Produces a script to incorporate only changes flagged Produces a script that will incorporate all changes between file2 and file3, but treat overlapping changes (that is, changes that would be flagged with in normal listing) differently. The overlapping lines in both files will be inserted by the edit script bracketed by and lines. Produces a script that will incorporate only changes flagged , but treat these changes in the manner of option. The following command applies the resulting script to file1. EXTERNAL INFLUENCES
International Code Set Support Single- and multi-byte character code sets are supported. WARNINGS
Text lines that consist of a single period defeat Files longer than 64K bytes do not work. FILES
SEE ALSO
diff(1). diff3(1)
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