10-29-2014
It depends on how much input data you have.
The grep method is very fast if you have enough memory, but that is its limit... If file1 is too large, it's liable to run out of memory and grind to a halt, or just plain crash. I wouldn't trust it with a file1 larger than a hundred or two megabytes. (file2 can be any size, though.) You should be doing grep -v -F -f file1 file2 by the way -- the -F makes sure the lines are all considered raw, instead of being used as regular expressions.
The sort method can reliably tolerate any size of input (though I would have used comm -1 -3 rather than diff).
So all else being equal, I'd use the sort method and worry less.
Last edited by Corona688; 10-29-2014 at 02:24 PM..
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NAME
diff - print differences between two files
SYNOPSIS
diff [-c | -e | -C n] [-br]file1 file2
OPTIONS
-C n Produce output that contains n lines of context
-b Ignore white space when comparing
-c Produce output that contains three lines of context
-e Produce an ed-script to convert file1 into file2
-r Apply diff recursively to files and directories of
EXAMPLES
diff file1 file2 # Print differences between 2 files
diff -C 0 file1 file2
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diff -C 3 file1 file2
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diff -c file1 file2 # Same
diff /etc /dev # Compares recursively the directories /etc and /dev
diff passwd /etc # Compares ./passwd to /etc/passwd
DESCRIPTION
the same name, when file1 and file2 are both directories" difference encountered"
Diff compares two files and generates a list of lines telling how the two files differ. Lines may not be longer than 128 characters. If
the two arguments on the command line are both directories, diff recursively steps through all subdirectories comparing files of the same
name. If a file name is found only in one directory, a diagnostic message is written to stdout. A file that is of either block special,
character special or FIFO special type, cannot be compared to any other file. On the other hand, if there is one directory and one file
given on the command line, diff tries to compare the file with the same name as file in the directory directory.
SEE ALSO
cdiff(1), cmp(1), comm(1), patch(1).
DIFF(1)