How to display only different rows using diff (bash)

a.txt:

1;john;125;3
1;tom;56;2
2;jack;10;5

b.txt:

1;john;125;3
1;tom;58;2
2;jack;10;5

Use comm:

comm -13 a.txt b.txt 
1;tom;58;2

The command line options to comm are pretty straight-forward:

-1 suppress column 1 (lines unique to FILE1)

-2 suppress column 2 (lines unique to FILE2)

-3 suppress column 3 (lines that appear in both files)

Here's a simple solution that I think is better than diff:

sort file1 file2 | uniq -u

sort file1 file2 concatenates the two files and sorts it
uniq -u prints the unique lines (that do not repeat). It requires the input to be pre-sorted.

Using group format specifiers you can suppress printing of unchanged lines and print only changed lines for changed

diff --changed-group-format="%>" --unchanged-group-format="" file1 file2

Assuming you want to retain only the lines unique to file 2 you can do:

comm -13 file1 file2

Note that the comm command expects the two files to be in sorted order.

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