You could use file(1) magic to check if a file is indeed a compressed file before trying to uncompress. For Perl there are File::MMagic and File::LibMagic among other modules to check file MIME type.

In reply to Re: How do you get IO::Uncompress::Gunzip to error if the input file isn't a GZ file? by parv
in thread How do you get IO::Uncompress::Gunzip to error if the input file isn't a GZ file? by sectokia

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