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Unix/Linux OS/External and internal commands


Hi Dylan i want to know some background information that when we are having a internal commands already in Unix and that too gives better performance when we compared it with external commands,so why we need external commands.
what is the need of going from internal to external commands,and from where external commands came.

Your question appears in the question pool so I'm thinking about it (in addition to the person you sent it to).  Can you explain the difference between an "internal" and an "external" command?  Nearly all "commands" are executed in a shell so are "external" to the kernel.  There's more than one shell for each different Unix/Linux variant.  An executable script is often called "command".  This is an executable text file that's run by the shell and is written to run using syntax for that shell.  A binary file (non-text) can be written in anything that's compiled or that's stored in the file as text and is converted into byte code by an interpreter.

Given this perspective nothing is "internal" and there isn't much you can do with a kernel that has no shell.

Perhaps your use of "internal" and "external" are different; thus I've asked you for their meaning.  

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John Crout


Answers about hardening, command-line operation,boot/start-up, reconfiguring the kernel, debugging, installing/removing packages. Interfacing with Windows. Most questions about building from source.


Been learning how to do these things since 1982.

Association for Computing Machinery, Information Systems Security Association

BSEE, Electrical and Computer Engineering

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