[Linux] About PATH

I will describe the terminal command PATH.

What is PATH?

A command to add a command search path. The command search path is a path that searches for the command executable file.

$ ls

For example, suppose you run $ ls, which references folders and files as above, and you have an executable file with the same name, ls, under the / bin directory. Since $ ls is executing the command without specifying the path, the shell will find the executable file corresponding to the command from each directory.

This path to find is called the command search path, and you can add this path with the PATH command.

How to check the command search PATH

You can check it with $ echo $ PATH. In a certain environment, it will be displayed as follows.

$ echo $PATH

The paths are separated by : The six / usr / local / bin, / usr / bin, / bin, / usr / sbin, / sbin, and/ usr / local / sbinare the search command path. It is set.

How to check the storage location of the command execution file

You can check it with $ which ls. The execution result is as follows.

$ which ls

#Execution result

When an executable file with the same name exists in multiple search command paths

In this case, it has priority and is executed from the one on the left output by $ echo $ PATH. For example, in the following cases

$ echo $PATH

It is executed from / usr / local / bin. The priority is / usr / local / bin / usr / bin/ bin / usr / sbin/ sbin/ usr / local / sbin.


To add PATH, write it in the .bashrc or .bash_profile file in the ʻexport PATH = $ PATH: command search path` format you want to add.

Actually add PATH and try to pass


export PATH=$PATH:Command search path you want to add


export PATH=$PATH:Command search path you want to add

The file that describes the PATH can be either .bashrc or .bash_profile.

$ source ~/.bashrc
$ source ~/.bash_profile

If you do not execute each described file with the source command, the path will not pass.

What is the export command?

Display and set environment variables.

Display environment variables

export -p

#Output result(Only a part is described)
declare -x PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
declare -x LANG="ja_JP.UTF-8"
declare -x SHELL="/bin/bash"

The set environment variables are displayed.

Setting environment variables

For example, to set the environment variable $ ULB, set as follows.

$ export ULB=/usr/local/bin

$ echo $ULB
/usr/local/bin #Output result

I have confirmed that it is set with $ echo $ ULB.

ls /usr/local/bin
ls $ULB

Both commands produce similar results.

Override environment variables

$ echo $ULB
/usr/local/bin #Output result

$ export ULB=/u/l/b

$ echo $ULB
/u/l/b #Output result

You can also overwrite environment variables as described above.

Delete environment variables

It can be deleted with the ʻunset` command.

$ unset ULB #[$]Does not have to be entered.

$ echo $ULB
#Nothing is output.

Increase the priority of the command search path to be added

$ export PATH=Command search path you want to add:$PATH

The command search path has the highest priority from the left, so describe it like this.

Reference URL

Introduction to Linux ~ What is "passing through" ~ https://qiita.com/Naggi-Goishi/items/2c49ea50602ea80bf015

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