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Many students may have a headache when they see the environment variables. They do not know how to match and do not know what to change

Once you want to configure environment variables, you can browse the Internet and copy them randomly

So I’m going to summarize the environment configurations and commands I use in my work, based on my knowledge

If there’s anything wrong, the big guys are spitting in the comments section

I use a Mac, most of the following introduction is based on Mac and Linux, Windows brother for reference only

SHELL Environment introduction

First we need to introduce the SHELL environment

We open the environment inside the black box that appears in “terminal” (some of you use iterm2 or other terminal tools) and call it the SHELL environment

There are many different SHELL environments, the most common being Bash and ZSH

Bash and ZSH

In early Macs, the default shell environment was bash

On today’s new Macs, the default shell environment is ZSH

Of course, if you don’t know what SHELL environment you are in, you can use the following command to check

echo $SHELL
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Older Macs that install the new OS will prompt you to switch if you haven’t modified ZSH

So here we see a command prompt that suggests switching to ZSH

Switch command

chsh -s /bin/zsh
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How do I check what shells are available on this machine

cat /etc/shells
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Configuration files for environment variables

So, let’s look at the environment variable configuration file

What are configuration files for environment variables?

I think the pendulum concept is a little bit confusing, so I think in terms of functions.

To put it more simply, environment variable configuration files are the files that terminal tools load by default when you open terminal tools.

For example, suppose you create a new A file

The a file is loaded by default every time the terminal is opened

The environment variables configured in file A are then loaded into the shell environment

So at this point, you think of the A file as a configuration file for environment variables, why not

Environment variable configuration file

System profile and user profile

There are two types of configuration files, one for the entire system and one for the user

system	The user
/etc/profile	~/.bashrc
/etc/bashrc	~/.zshrc
—	~/.bash_profile

The /etc/directory is the main configuration directory

We can see that the system-level ones are all under /etc/etc

The user configuration is under ~, because CD ~ actually goes to the corresponding user name directory

Load order

Basically load the system first, and then load the user

(There is a complete sequence here, but I have not verified it, so I am afraid to copy and paste it.)

You don’t have to worry about the load order, because normally, we only modify the user’s environment variable file. Conflicts and so on rarely occur in our daily work.

Different variable files in different environments

The following files are user files, that is, ~/.xxx

When we look up various environment variable configurations online, we can see that there are different files that you need to change

Some will let you change.bash_profile, some will let you change.bashrc, some will let you change.zshrc

First, we need to use the echo $SHELL described above to see what the current SHELL environment is

Bashrc is a sibling of bash, usually by modifying either ~/.bash_profile or ~/.bashrc

ZSHRC is a cousin of ZSH, and generally modifies ~/.zshrc files

No files

What?

What will you do without these documents?

Create one manually

cd ~
Create file manually
touch .bash_profile
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There you have it

So once it’s created, the terminal is going to read it, you don’t need to do anything else, right

The environment variable

That’s the environment variable configuration file, so let’s talk about environment variables

What are environment variables

To view the current environment variables, run the following command

echo $PATH
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The idea is to inject some paths ahead of time so that we can execute some executables quickly so that we don’t have to find a specific path every time.

Maybe some of you don’t understand this very well.

Here are two examples:

Example 1: Configuration of a FLUTTER environment variable

When configuring the Flutter environment, we can see that after git Clone the Flutter project

You can see that there is an executable named flutter under the flutter/bin/ directory

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As an extra point, if you download anything that requires environment variables to be configured, there will always be a bin directory, and the executable files will always be in the bin directory. This is a general rule.

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Generally, we can determine whether the flutter environment is successfully installed by directly executing the flutter -V at the terminal to see if there is a response

What if we didn’t configure the environment variables and just used the bin/flutter to execute this command?

The answer, of course, is yes.

In other words, after configuration, the effect is:

flutter -v
# is equivalent to
/Users/xing.wu/Documents/environment/flutter/bin/flutter -v
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To configure environment variables is to configure the path before the flutter into the default shell path.

The/Users/xing wu/Documents/environment/flutter/bin/configuration to the path

Configuration method

Locate the environment variable configuration file and add it

export PATH=/Users/xing.wu/Documents/environment/flutter/bin:$PATH
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In other words, other environment variable configurations can be configured in this way without special commands

export PATH=xxxx:$PATH
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After that, you can choose to reopen a new terminal or use the source command to read the environment configuration file

The source command is a built-in shell command for reading and executing commands from a file in the current shell session

Other environment variable files are modified by themselves
source ~/.zshrc
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Example 2: NPM global installation package

I’m using an NVM installed Node environment, so the path I add to the path will take NVM

1. First, let’s take a look at which packages I have installed globally

You can see I have a global @vue/cli here

So I can use vue Create Project to create the project

2. So where is the path to the vue

which vue

You can see that the path to/Users/xing wu /. NVM/versions/node/v15.14.0 / bin/vue

Scroll forward to see the result of our echo $PATH

/ Users/xing wu/Documents/environment/flutter/bin: / Users/xing wu /. NVM/versions/node/v15.14.0 / bin: / opt/homebrew/bin: / opt/h omebrew/sbin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Apple/usr/binCopy the code

Can see/Users/xing wu /. NVM/versions/node/v15.14.0 / bin: we joined the environment variable, so can directly use the vue related commands, other libraries in the same way.

We can look at the bin directory

All shortcuts or ontologies to available executables associated with the NPM library are here.

At the end

What is the current SHELL on the Mac, what is the configuration file, and how is the path configured

I believe that the future of the environment configuration is not difficult to fall everyone ~

Here’s a quick question:

ZSHRC is not read by ~. Bash_profile. ZSHRC is not read by ~/.zshrc.

Leave your answers in the comments section