5. Comparing text

1. Let's create two test files:

   cat > file1.txt <<EOF
   a
   b
   c
   d
   EOF

   cat > file2.txt <<EOF
   b
   c
   d
   e
   EOF

2. We can compare them with comm:

   comm file1.txt file2.txt

   comm -12 file1.txt file2.txt

   In this case we are suppressing the columns 1 and 2.

3. A more complex tool is diff:

   diff file1.txt file2.txt

   With context:

   diff -c file1.txt file2.txt

   Unified format is more concise:

   diff -u file1.txt file2.txt

4. To create a patch file usually the options -Naur are used:

   diff -Naur file1.txt file2.txt > patchfile.txt

   cat patchfile.txt

   We can use the command patch to apply a patch file:

   patch file1.txt patchfile.txt

   cat file1.txt

   Now file1.txt has the same content as file2.txt.

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