Archiving and Compression
=========================

Archiving is the process of combining multiple files and directories into one file.
compression is the process of reducing the size of a file
(or an archived directory).


Here's an article touching on all of this in depth.
https://www.linuxjournal.com/article/9370


tar and gzip options and examples
---------------------------------

`tar [options] [archive-file] [file or directory to be archived]`

* -c : Creates Archive
* -x : Extract the archive
* -f : creates archive with given filename
* -t : displays or lists files in archived file
* -u : archives and adds to an existing archive file
* -v : Displays Verbose Information
* -A : Concatenates the archive files
* -z : zip, tells tar command that create tar file using gzip
* -j : filter archive tar file using tbzip
* -W : Verify a archive file
* -r : update or add file or directory in already existed .tar file


.. code-block:: bash

    # piping data (text or chars) through gzip, and reverse
    echo "hello world" | gzip -c > file.gz ; cat file.gz | gzip -d -c

    zcat file.gz 

    # is a shorthand for this

    cat file.gz | gzip -d -c

    gunzip file.gz # this command does stuff in-place



    # creat a tar.gz file
    tar -f /bits/data/logs.tar.gz -czv /bits/data/logs
    
    # extract a tar.gz gile
    tar -xzf logs.tar.gz
    
    # download file with a specified name
    wget -O drupal.tar.gz https://www.drupal.org/download-latest/tar.gz
    
    
    tar -xzvf drupal.tar.gz


    # list contents of an archive
    tar -tvf drupal.tar.gz

    drupname=$(tar -tf drupal.tar.gz | head -n 1 | sed 's/.$//')



Drupal Update process
---------------------

.. code-block:: bash

    # download file with a specified name
    wget -O drupal.tar.gz https://www.drupal.org/download-latest/tar.gz


    tar -xzvf drupal.tar.gz


    # list contents of an archive, not 
    tar -tvf drupal.tar.gz


    drupbase=/home/mk/drupal

    cd $drupbase

    time_stamp=$(date +%s)

    mv drupal drupal_back_$time_stamp

    filename=drupal_$time_stamp.tar.gz
    wget -O $filename https://www.drupal.org/download-latest/tar.gz

    drupname=$(tar -tf $filename | head -n 1 | sed 's/.$//')

    tar -xzf $filename

    mv $drupname drupal


    

Other Tricks
------------

When creating backup you can include datetime (date time) stamp (timestamp) in the filename

.. code-block:: bash

    pg_dump -h nuc -U redmine redmine > /bits/data/backup/redmine$(date +%s).sql