tar: prepare for examples

1 
1 2.6.1 Preparing a Practice Directory for Examples
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1 
1 To follow along with this and future examples, create a new directory
1 called 'practice' containing files called 'blues', 'folk' and 'jazz'.
1 The files can contain any information you like: ideally, they should
1 contain information which relates to their names, and be of different
1 lengths.  Our examples assume that 'practice' is a subdirectory of your
1 home directory.
1 
1    Now 'cd' to the directory named 'practice'; 'practice' is now your
1 "working directory".  (_Please note_: Although the full file name of
1 this directory is '/HOMEDIR/practice', in our examples we will refer to
1 this directory as 'practice'; the HOMEDIR is presumed.)
1 
1    In general, you should check that the files to be archived exist
1 where you think they do (in the working directory) by running 'ls'.
1 Because you just created the directory and the files and have changed to
1 that directory, you probably don't need to do that this time.
1 
1    It is very important to make sure there isn't already a file in the
1 working directory with the archive name you intend to use (in this case,
1 'collection.tar'), or that you don't care about its contents.  Whenever
1 you use 'create', 'tar' will erase the current contents of the file
1 named by '--file=ARCHIVE-NAME' ('-f ARCHIVE-NAME') if it exists.  'tar'
1 will not tell you if you are about to overwrite an archive unless you
1 specify an option which does this (⇒backup, for the information
1 on how to do so).  To add files to an existing archive, you need to use
1 a different option, such as '--append' ('-r'); see ⇒append for
1 information on how to do this.
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