LINUX VS UNIX ? POSIX

Why are we comparing these two, are not they purely different with no similarity? No they have similarities which push you to a confusion about these two things. So lets talk about the similarities first.

  1. Commands (ls, cp, mv, chmod, kill .. many more)
  2. Directory structure
  3. Philosophy of everything is file

List of Unix Based OS

  1. HP-UX
  2. IBM-AIX
  3. BSD (Berkeley Software Distribution discontininued propietory to start FreeBSD)
  4. NetBSD
  5. Oracle Solaris (Earlier SunOS)

For a recent list of UNIX certified products visit the UNIX owner The Open Group Page Link.

These above listed based on UNIX but not only based on UNIX but also certified UNIX system. without certification one cant write unix but unix-like.

List of Unix like OS

  1. FreeBSD
  2. NetBSD
  3. 386BSD
  4. DragonflyBSD

Unix How it became a Standard from a Non Portable single tasking platform (Not even an OS)

Unix initially it was a non-portable non multitasking platform for programmers, with it time it gained portability , multitasking and multiuser too. After adoption by other vendors it started compiling a specification standard known as SUS (Single Unix Specification).

Q: Linux ? How can we identify ?

Ans: The linux kernel, if its based on a linux kernel then its linux. Linux on the otherhand is UNIX derivative so listed as UNIX-LIKE operating system.

Difference between Unix and Linux in 5 points

  1. Both Linux and Unix initially popular as a Operating system but later unix gained popularity as a standard and Linux as a kernel for an UNIX-like OS.
  2. Linux itself is a Unix-Like Operating system, so it can be called a derivative of unix.
  3. Linux is free open source licensed under GNU, but unix is a proprietary software and all unix certified softwares are propietory. The certification cost few thousand dollars.
  4. Unix certified systems should follow rules set by SUS(single unix specification) and Linux systems have similar rules for compatibility known as POSIX standrads.
  5. The Linux standard POSIX is implemented by IEEE and UNIX standard is implemented and certified by The Open Group.
Unix history

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