The foundation of UNIX was set with several key elements:
The UNIX file system??”After creating the structure that allowed levels of subdirectories
(which, for today??™s desktop users, looks like folders inside of folders), UNIX could be
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Starting with Linux 1
used to organize the files and directories in intuitive ways. Furthermore, complex methods
of accessing disks, tapes, and other devices were greatly simplified by representing
those devices as individual device files that you could also access as items in a directory.
Input/output redirection??”Early UNIX systems also included input redirection and
pipes. From a command line, UNIX users could direct the output of a command to a file
using a right arrow key (>). Later, the concept of pipes (|) was added where the output
of one command could be directed to the input of another command. For example, the
command line
$ cat file1 file2 | sort | pr | lpr
concatenates (cat) file1 and file2, sorts (sort) the lines in those files alphabetically, paginates
the sorted text for printing (pr), and directs the output to the computer??™s default
printer (lpr). This method of directing input and output enabled developers to create
their own specialized utilities that could be joined with existing utilities.
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