How to ignore timestamp of the files while performing diff operation

Question

I created a file named me.txt with text

This is dummy text

Then I made a TAR out of it and named me.txt.tar.

Now after a minute I again created a file with exactly same name and the text (basically I just did touch me.txt), then made TAR out of it called me2.txt.tar.

Technically both the tars have same file with same file contents but time of creation of file me.txt is different. But the diff tool is saying:

Binary files me.txt.tar and me2.txt.tar differ

This is because of reason of timestamp difference of file creation. But I just want to compare the contents of file and need to ignore the timestamp & hence I expect no output from the diff.

Please help me to ignore the timestamp of the files inside a TAR or JAR etc. as my concern is towards the contents of files.

• The commands I used are :

  $ echo "This is dummy text" > me.txt
  $ tar -cvf me.txt.tar me.txt
  (After 1 minute or so..)
  $ touch me.txt 
  $ tar -cvf me2.txt.tar me.txt
  $ diff me.txt.tar me2.txt.tar
  

• output:

  Binary files me.txt.tar and me2.txt.tar differ
  

Even diffoscope gives similar output.

Answer 1

Since you want to compare the contents of the files in your archives, and not the metadata in the archives themselves, you should compare the contents. Assuming the files are stored in the same order in all archives,

diff -u <(tar xOf me.txt.tar) <(tar xOf me2.txt.tar)

For JARs, you’d use unzip:

diff -u <(unzip -c file1.jar) <(unzip -c file2.jar)