One of this blog follower asked us that whatâs the difference between absolute and relative path?
To understand this we have to know what is a path in Linux.
### What is a path?
A path is a unique location to a file or a folder in a file system of an OS. A path to a file is a combination of / and alpha-numeric characters.
What is an absolute path?
An absolute path is defined as the specifying the location of a file or directory from the root directory(/). In other words we can say absolute path is a complete path from start of actual filesystem from / directory.
### Some examples of absolute path:
```bash
/var/ftp/pub
/etc/samba.smb.conf
/boot/grub/grub.conf
```
If you see all these paths started from / directory which is a root directory for every Linux/Unix machines.
### What is the relative path?
Relative path is defined as path related to the present working directory(pwd). Suppose I am located in /var/log and I want to change directory to /var/log/kernel. I can use relative path concept to change directory to kernel
changing directory to /var/log/kernel by using relative path concept.
> $ pwd/var/logcd kernel
Note: If you observe there is no / before kernel which indicates itâs a relative directory to present working directory.
Note: We can use an absolute path from any location where as if you want to use relative path we should be present in a directory where we are going to specify relative to that present working directory.
Examples of relative path and absolute path for the same operation.
# Basic Linux Command
## help
- Man: an interface to the on-line reference manuals
In the absolute mode, permissions are represented in numeric form (octal system to be precise). In this system, each file permission is represented by a number.
- r (read) = 4
- w (write) = 2
- x (execute) = 1
-– (no permission) = 0
With these numeric values, you can combine them and thus one number can be used to represent the entire permission set.
| Number | Permission |
|--------|------------|
| 0 | — |
| 1 | –x |
| 2 | -w- |
| 3 (i.e. 2+1) | -wx |
| 4 | r– |
| 5 (i.e. 4+1) | r-x |
| 6 (i.e. 4+2) | rw- |
| 7 (i.e. 4+2+1) | rwx |
most commonly used:
755 644 600 640
Can you guess the file permission in numbers on agatha.txt file in our example so far? That’s right, it’s 764.
Now that you know what number represents which permission, let’s see how to change file permission using this knowledge.
Suppose you want to change the file permission on agatha.txt so that everyone can read and write but no one can execute it? In that case, you can use the chmod command like this:
> $ chmod 666 agatha.txt
## Danger : if a folder has not the X (executable) right => you cannot open it.
-R for recursive on folder
If you list agatha.txt now, you’ll see that the permission has been changed.
> -rw-rw-rw- 1 abhishek abhishek 457 Aug 10 11:55 agatha.txt
- Chown: change file owner and group
> $ sudo chown marie:marie agatha.txt
> -rw-rw-rw- 1 marie marie 457 Aug 10 11:56 agatha.txt
To create a symbolic link to target file from link name,
you can use the ln command with -s option like this:
> ln -s target_file link_name
The -s option is important here. It determines that the link is soft link. If you don’t use it, it will create a hard link. I’ll explain the difference between soft links and hard links in a different article.
