I'm a bit confused about the command types in Linux. There are internal (built-in) commands and external (pre-installed) commands, right? I'm trying to figure out which category the mkdir command falls into. I've seen some sources stating it's internal, but it seems to be pre-installed as well. When I type 'type mkdir' in the terminal, it outputs '/usr/bin/mkdir'. Shouldn't it indicate that it's a built-in command instead?
4 Answers
mkdir is likely built into BusyBox, which can be customized, but it isn’t part of your shell directly. So, both sides of the argument can be correct!
The /bin directory has the basic commands as defined by the POSIX standard. In short, these are considered basic commands. It may help to remember that most commands aren’t strictly part of the command-line interface itself, as there's only a handful of internal commands.
If you can list a command using 'help xyz', then it's considered a built-in command. That being said, there are commands that have both a built-in and an external version, often with documentation noting they're built-in on your system.
Technically, many commands are considered internal since they're actually programs. Just to clarify, the BASH manual lists specific internal commands that BASH manages directly, such as alias, echo, and type.
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