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I was wondering about a simple event that occurred while I was installing node version manager on my 64bit Amazon Linux 2014.09 Web Server. When I executed this install script

curl https://raw.githubusercontent.com/creationix/nvm/v0.23.3/install.sh | bash

NVM installed onto my filesytem at ~/.nvm/

What is the significance of the ~/.nvm as opposed to ~/nvm ? Specifically, what does the ' . ' mean before nvm?

This is especially important because when I execute " ll " in the ~/ folder, I do not see any files. However, when I execute cd ~/.nvm , I am taken to the ~/.nvm folder.

Also, in order to get nvm working in the terminal, I had to "source" the nvm.sh file in this way

source ~/.nvm/nvm.sh

What did this source command accomplish?

Note: everything is working, this is just a curiosity I would like to understand better so that I feel more comfortable with server configurations etc.

Thanks a bunch!

deusofnull
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1 Answers1

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The character . at the beginning of the filename makes it hidden.
To see an hidden file from shell you can do ls -a (or ls -A).

Note the differences:

 .myfile.sh       # hidden file
 .   myfile.sh    # source the file myfile.sh

source (or .) are internal command of bash. You can have access to their definition with help.

With the command type you can understand if a command is a built-in shell or not.

E.g. the command type source /bin/ls will answer

source is a shell builtin
/bin/ls is /bin/ls

Then you can ask to the system information about the commands respectively with help or man.

From help source you can read

source: source filename [arguments]
Execute commands from a file in the current shell. Read and execute commands from FILENAME in the current shell. The entries in $PATH are used to find the directory containing FILENAME. If any ARGUMENTS are supplied, they become the positional parameters when FILENAME is executed.

From man ls

-a, --all
do not ignore entries starting with .

Hastur
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  • Is there a command for making a file un-hidden besides " cp -Rf ~/.file/ ~/file/ ? Will a file being hidden / un-hidden effect its functionality? – deusofnull Feb 18 '15 at 15:05
  • I didn't understand fully. If you do `cp -Rf ~/.file/ ~/file/` you will copy the directory named `.file` and all hidden or not subdirectories in the directory named `file` if it exists, else in your home (`~`). Instead if `file` is a file you will receive as answer an error `cp: impossible .... .file/ is not a directory` – Hastur Feb 18 '15 at 15:17
  • Yeah, file was just a place holder. In this instance, the command would be `cp -Rf ~/.nvm/ ~/nvm/ ` Would this change the functionality of nvm if you "source" it after this move? – deusofnull Feb 18 '15 at 15:35
  • About the action of source, give it a look [to this](http://superuser.com/questions/46139/what-does-source-do). To _`source`_ is like to execute all the script as you were writing that commands in the present shell. You question should be: __what will it happens if I change the name in which is installed a script?__ ;) The answer is __it depends__ from the script. It's possible you will have problem. I cannot know it from here, but for example each call with absolute path will search it in `~/.nvm/whateverelse`... and not in you new directory `~/nvm/whateverelse`. – Hastur Feb 18 '15 at 15:47
  • Thanks for the link! So it is probably best to leave it in the hidden file... You rock – deusofnull Feb 18 '15 at 15:58
  • You're welcome. Continue to be curious, [focused](http://garfield.dale.ro/ga931025.gif) and you will rock even more in _a blink of an eye_! ;) – Hastur Feb 18 '15 at 16:19
  • If you want the configuration files to be visible, add a link `ln -s ~/.nvm ~/nvm`. Note that there are two implications of hidden files: as well as not appearing in a default directory list, they also do not get expanded for `*`. To show all files in the current directory you need `echo .* *`, or `echo .[^.]* *` if you want to exclude `.` and `..`. – AFH Feb 18 '15 at 16:30
  • Do you really went to do that, @deusofnull? Because those hidden files and directories are usually configuration files for that the user can change. When a program starts (like `nvm`), it usual loads some basic settings that are part of the program (compiled into it). Then it reads a file (something like `/etc/nvm`) that the system admin (root) can use to make changes for all users on the system. Lastly the program reads configs for the user, that overrides all others (usually `~/.nvm`). Notice that the namen is important. And it's nothing special with the `.`, it is just not printed by `ls`. – Anders Feb 18 '15 at 17:18
  • Ok, so the ` . ` just means ls doesn't print it, that's fine. I might do that sym link solution though, just for visibility if it wouldn't impact functionality. Is there a command for listing hidden files or do you just have to make note of it somewhere? – deusofnull Feb 18 '15 at 17:36
  • @deusofnull Yeah be curious but read carefully the answers too: `ls -a`, `ls -A`, `echo .*`, `echo .[^.]* *` ... ;-) and man `ls` for all the options... I forget `tree -a` if you have the command `tree` installed. – Hastur Feb 18 '15 at 17:59
  • Sweet! wow I didn't know all this about ll & ls! Thanks! – deusofnull Feb 18 '15 at 18:15
  • If your wondering why it's hidden, because you don't really go into the directory. You access it via commands. There is no point of having it visible, just clutters up your home directory. – Karl Morrison Mar 26 '15 at 13:49