When creating filepaths and URLs, I noticed that many times the path starts with ./ or ~/.
What is the difference between filepaths that start with ./ and ~/?
What do each of them mean?
For the sake of completeness ...
Just path is a file or directory named path in the current directory.
./path is a file or directory named path in the current directory, with the directory spelled out. The dot directory . represents the current directory, and path is the name of the file or directory within this directory.
~/path is a shorthand for $HOME/path where $HOME is a variable which refers to your home directory. Typically your home directory will be somewhere like /home/you or /Users/you where you is your account name. (The command echo "$HOME" will display your home directory.) The expanded value is an absolute path (unless you have messed up the value of $HOME thoroughly), as indicated by the initial slash.
/path is an absolute path which refers to a file or directory named path which is in the root directory /. Every file on Unix is ultimately somewhere in the directory tree which starts with the root directory.
A file name which begins with $ includes the value of a shell variable in its name (like for example $HOME above); you have to know the value of that variable to determine whether it ends up containing a relative or an absolute path. Similarly, ~ at the beginning of a file name gets replaced ("expanded") by the shell to a different string, as outlined above.
(Technically, it's possible for a file name to begin with a literal dollar sign or tilde, too; you would then have to quote or backslash-escape that character to avoid having the shell expand it to something else. This is rather inconvenient, so these file names tend to be rare in practice.)
In the following exposition, we refer to the result of any such replacements, and ignore the complication of possible quoting.
Every file name which begins with / is an absolute path (aka full path) which explains how to reach a particular node starting from the root directory. For example, /var/tmp/you/reminder.txt refers to a file or directory reminder.txt (probably a file, judging from the name; but Unix doesn't care what you call your files or directories) which is in the directory you which is in the directory tmp which is in the directory var which is in the root directory.
Every file name which doesn't begin with / is a relative path which indicates how to reach a particular file or directory starting from the current directory. The special directory .. is the parent directory (that is, the directory which contains this directory) and the special directory . is the current directory. So path/there refers to the file or directory there inside the directory path in the current directory; and (hover the mouse over the gray area to display the spoiler)
there/.././and/back/.. is a (wicked complicated) way to refer to the directory and in the current directory, where we traverse the there directory and then move back to the current directory; then stay in the current directory; then refer to the directory back inside the directory and, but then move back to the parent directory of that, ending up with ./and.
In addition to ~/ for the current user's home directory, some shells and applications allow the notation ~them/ to refer to the home directory of the user account them. Also, some web server configurations allow each user to have a public web site in their directory ~/public_html and the URL notation http://server/~them/ would serve up the site of the user account them for outside visitors.
The current directory is a convenience which the shell provides so you don't have to type long paths all the time. You can, if you want to.
/bin/ls /home/you/Documents/unix-101/directories.txt
is a longwinded but perfectly valid way to say (assuming you are in your home directory),
ls Documents/unix-101/directories.txt
You could also say
cd Documents/unix-101
ls directories.txt
and until you cd again, all your commands will run in this directory.
See What exactly is current working directory? for a longer exposition of this related concept.
A "directory" is sometimes called a "folder" by people who are not yet old enough to prefer the former.
Tangentially, don't confuse the directory name . with the Bourne shell command which comprises a single dot (also known by its Bash alias source). The command
. ./scriptname
runs the commands from the file ./scriptname in the context of the current shell instance, as opposed to in a separate subshell (which is what just ./scriptname does). In other words, this command line invokes the dot command on a file scriptname in the dot directory.
The Bourne shell (and derivatives like Bash, Zsh, etc) use single quotes to prevent variable expansion and wildcard expansion, and double quotes to permit variable expansion, but inhibit wildcard expansion in a string. The quoting rules on Windows are different, and generally use double quotes to keep whitespace-separated values as a single string (and % instead of $ for variable substitutions).
./ means "starting from the current directory". . refers to the current working directory, so something like ./foo.bar would be looking for a file called foo.bar in the current directory. (As a side note, .. means refers to the parent directory of the current directory. So ../foo.bar would be looking for that file one directory above.)
~/ means "starting from the home directory". This could have different meanings in different scenarios. For example, in a Unix environment ~/foo.bar would be looking for a file called foo.bar in your home directory, something like /home/totzam/foo.bar. In many web applications, ~/foo.bar would be looking for a file called foo.bar in the web application root, something like /var/http/mywebapp/foo.bar.
./ is the current directory
~/ is the home directory of the current user
./ means that path is relative to your current position.
~/ means that path is relative to your home directory.
I will explain a simple example of it. As developers mentioned:
./ is current directory.
~/ is the home directory of the current user.
How both of the file path expressions can help us? Suppose you want to execute a script (.sh) and you're in the same directory where file exists then you can simply do it ./filename.sh
I mostly use ~/ to access my home directory files like .bashrc when I want to add any config in it. It's easier since the file path expression (for home directory) feels much easier and makes accessibility to the file from anywhere, without worrying about the path or changing the path.
. represents current directory
.. represents the parent directory
~ represents the home directory for the current user. Home directory is also represented by HOME env variable. you can do echo $HOME on the shell to see it.
These are generally used to specify relative paths. The / in the end of each notation is a separator that you can use when using these notations together.
Ex:
$ cd ../.. # Go 2 directories backwards
$ cd ~ # Takes you to $HOME directory
$ cd . # Does nothing :) As it literally means go to the directory that you are already present in.
$ cd ~/dir1 $ go to `$HOME/dir1`
On Unix, in any directory if you do ls -a you would see that . and .. will be mentioned (even for empty directory). Like mentioned, these have special meaning and are generated by default in Unix systems and are generally helpful to specify relative paths (i.e, path to a different directory relative to your current directory)
cd command is harmless. So, just play around by combining notations with cd command. You will eventually get a grip of them.
Im having trouble in Bash.
I have plain files in a directory on my desktop. I am trying to move them into a subdirectory within that directory using: mv "Filename" /"Directoryname"
However when I use this command, I get an error telling me that the permission was denied.
I am set as the owner of both directories and have should have full permissions. If there is anything I need to provide you to make it easier for you to help me, I will be glad to help.
Try mv filename subDirectoryName/.
By placing / in front of the directory name in a move sequence, you're telling the shell that you would like it to be placed in a high level folder named /folder.
What you want is a sub-directory within your current directory. As you would usually move directories in bash, ../ goes up one directory, and directory/ implies you are moving into a folder that is within your current directory.
I am new to shell scripting
Copy one directory to another directory, if target directory already exist? how to rename target directory ?
for example i have a directory (red) need to copy another directory (org), target directory (org) have already red directory at that time need to rename it.
using shell scripting?
Copy a directory even if it exists and recursively:
cp -rf source target
Rename a directory
mv oldname newname
I've been working on a script but always with a fixed directory (/opt/mw/script).
I need to change that to be able to execute the script from any directory.
I think I will need to add a "." at the beginning of the line to be able to execute the script?
For example ./mw/script
Is this correct?
Thanks
You already can execute that script from any directory with that absolute file path. It's the relative file paths (that start with ./ or ../) that can only be executed from a specific directory.
You need to add the "." if the script is in the current directory (e.g. ./script), but it is optional if the script is already inside another directory (e.g. mw/script).
Also notice that if your script contains relative references to other files and directories, you may need to use this trick to properly refer to them from any directory.
For instance, consider the following script using absolute paths:
#!/bin/bash
# lists all files in this directory
ls /opt/mw
If it is converted to relative paths as follows:
#!/bin/bash
# lists all files in this directory
ls mw
Then this script will only work if you run it from its own directory (e.g. cd /opt/ && ./script).
But then you can generalize it like this:
#!/bin/bash
SCRIPT_DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
# lists all files in this directory
ls $SCRIPT_DIR/mw
Now the script works even when executed from another directory.
I have written a bash script which is dependent on current folder structure,
What should I do to make it runnable in any other folder(become portable)?
let me explain more: I want the script to delete all the files in current directory that the script is running,
or to delete all the files that are in the parent folder,
what is the solution?
cd "$(dirname "$0")"
Add this to the top of your script to have it cd to the directory the script is installed at. Then you can use relative paths and they'll be relative to the script dir and not the user's pwd.
If for whatever reason dirname isn't available, here's an equivalent statement that uses basename instead.
cd "${0%%/$(basename "$0")}"
Don't use absolute paths in your script.
we need more information to give you a proper answer...BUT some tips if you need to make it portable are to store any files that you need on a network share and simply make a new folder off of / such as /temporaryScriptFolder/ and mount the network share to that empty folder, allowing you easy access to any resources that are necessary.