I have two gz files named 1.gz(315M) and 2.gz(2.6G). I use cat to merge the two files
cat 1.gz 2.gz > 3.gz
the size of 3.gz is 5.4G, I feel very surprised. How is this happened?
I cannot find the bioinformatics part of your question.
We believe that this post does not fit the main topic of this site.
Not bioinformatics. Please search/ask Stack Overflow
For this reason we have closed your question. This allows us to keep the site focused
on the topics that the community can help with.
If you disagree please tell us why in a reply below, we'll be happy to talk about it.
That happened because you didn't just concatenate 1.gz and 2.gz, you probably put 2.gz in twice. As pointed out in the comments, this isn't a bioinformatics question as written.