Linux - Difference between internal and external commands

In DOS, internal commands are the built-in commands that are already present in the command interpreter, whereas external commands are the commands that are external to the command interpreter and are stored in separate executable files on the disk.

Internal commands can be executed directly from the command prompt without invoking an external program. Some examples of internal commands in DOS include:

- DIR: used to display the contents of a directory
- CD: used to change the current directory
- MD: used to create a new directory
- RD: used to remove a directory
- TYPE: used to display the contents of a text file
- COPY: used to copy files from one location to another within the same disk.

On the other hand, external commands are executable files stored on the disk, which need to be invoked explicitly by typing their name at the command prompt. Some examples of external commands in DOS include:

- FORMAT: used to format a disk
- CHKDSK: used to check the integrity of a disk
- EDIT: used to open a text editor
- XCOPY: used to copy files and directories from one disk to another.

In summary, internal commands are part of the command interpreter itself, whereas external commands are separate executable files that need to be loaded before they can be executed.

Mohmmad arman 05-13-2023

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dev k panchal 11-16-2021

Internal commands are the built in commands of the shell. Which means that when you execute an internal command, no process will be launched to execute the command. Therefore the speed of executing an internal command will be very high. Example – cd,pwd,echo etc.

External commands are those command which are stored as a separate binaries. Shell starts separate sub-process to execute them. Most external commands are stored in the form of binaries in /bin directory. To execute external command shell check $PATH variable . If command present in the location mentioned in $PATH variable shell will execute it , otherwise it will give error.
example – ls,mv,cat etc.

type utility can be used to check whether a command is internal or external.
if the command is internal, the output will say that the command is shell builtin. If the command is external, the output will give you the path to the command.

krish 04-25-2014

nternal commands are the commands that are executed directly by the shell. These commands will not have a separate process running for each.External commands are the commands that are executed by the kernal. These commands will have a process id running for it.
Since ls is a program or file having an independent existence in the /bin directory or /user/bin, it is branded as an external command. Most commands are external in nature, but there are some which are not really found any where, and some which are normally not executed even if they are in one of the directories specified by PATH

Usama Jawaid 10-16-2012