UNIX invented it, BSD and Linux gave it to the world

Everything is a file is very successful paradigm in the UNIX/Linux communities which has allowed the kernel to simplify and uniformize how it uses devices which are exposed to the user as files. All files are treated as a bag of bytes. Reading/writing from a file is straightforward.

Besides actual data storage a lof ot fruitful exaptation has been derived from this paradigm and from the UNIX/Linux file system conventions:

• Files, folders, symlinks, hardlinks, named pipes (fifo), network pipes, devices
• Applications which handle readable files and can work together well (ex.: lines separated with \n, columns separated with \t): less/more, tail, head, sort, split, join, fold, par, grep, awk, colum, wc, sed, tee
• Configuration management
• Application storage
• Library registry
• Disk cloning
  • Disk images for backup (dd)
  • Smaller than disk size images (skip unused space)
  • Compress disk images on the fly without storing the uncompressed version (dd | gz)
  • Restoring disk images from backups
  • Disk recovery — HDDs, CDs, DVDs, USB sticks etc. — when they have bad sectors or scratches
  • Creating bootable USB sticks from a raw image file or an ISO (dd again)
• Virtual filesystems
  • Mounting a raw image file or ISO as a filesystem
  • Mounting archives and compressed archives as a filesystem (tar, gz, bz, zip, rar)
  • Network filesystems look just like normal folders SAMBA, NFS
  • Using various network protocols as filesystems: HTTP, FTP, SSH
• Searching everywhere (find, grep, sed)

Plan9 from Bell Labs made it better

Current UNIX/Linux distros don’t implement this paradigm fully — ex.: network devices aren’t files — but some less known systems do (such as UNIX successor plan9 / inferno and their Linux correspondent glendix).

The plan9 project went onward in applying the paradigm for:

• Processes
  • Process management
  • Inter process communication
  • Client-Server network communication
• Network related issues:
  • Network interfaces are files
  • Access rights to network interfaces is based on filesystem access rights to symlinks pointing to interface files
  • The filesystem (9P) extends over the network as a network communication protocol
• Graphics interfaces and mouse IO

Other innovations it brought us (which got implemented in UNIX/Linux):

• UTF-8 / Unicode
• Filesystem snapshotting
• Union filesystems
• Lightweight threads