Bsrgvty

I'm new to Linux and was wondering if relative path can access more than one level.

For example:

/home/john/Desktop/Myfiles/text.txt

If i'm currently at ~/ can i jump to text.txt without having to write Desktop/Myfiles/ in my path ?

Yes, all paths can have multiple components. "Relative" paths don't begin with "/", and start looking in the current directory. "Absolute" paths begin with "/" and start looking at the root of the filesystem tree, also called "/".

So, you can use paths like this:

cd $HOME
ls Desktop/MyFiles/text.txt

or:

cd $HOME/Desktop/MyFiles
ls text.txt

In either case, ls /etc/passwd would refer to the same file.

Skipping parts of path cannot be done, that is you cannot do something like cd ~/.../Myfiles . Suppose you have /home/john/Desktop/Myfiles/ and /home/john/Documents/Myfiles. When you want to navigate to Myfiles, which one do you mean ? One in ~/Desktop or ~/Documents. Essential reason is because directory structure is organized into a tree, where each preceding element has to have a parent item. Thus, the question becomes who is the parent directory of Myfiles when there are two of them ?

However, there are several things that help navigating the long pathnames:

• save absolute path to variable. Say myfiles=/home/john/Desktop/Myfiles. When you start the shell, you already have $HOME special variable or you can use tilde expansion cd ~/Desktop/Myfiles


• 
  

  use pushd and popd. Shell has something known as "directory stack", which can be used to record a sequence of directories. For example, if I do

  
  
  

  $ pushd /etc
  /etc ~
  
  $ pushd /sys/class/backlight/intel_backlight/
  /sys/class/backlight/intel_backlight /etc ~
  
  $ pushd .
  /sys/class/backlight/intel_backlight /sys/class/backlight/intel_backlight /etc ~
  

  
  
  

  Notice that in dirstack the very first item indicates current working directory, while the second item remains unchanged even if you cd elsewhere. This is why pushd . was added. Now, if we navigate elsewhere, /sys/class/backlight/intel_backlight will be stored on the stack and we can always return to it.

  
  
  

  # navigate elsewhere after pushd .
  $ cd /var/log
  $ cd /usr/share
  # check what's in the stack
  $ echo $DIRSTACK[@]
  /usr/share /sys/class/backlight/intel_backlight /etc /home/ubuntuadmin
  # go to one of the directories on the stack
  $ cd $DIRSTACK[1]
  $ pwd
  /sys/class/backlight/intel_backlight
  # remember that very first item changes, it's the current working directory
  $ echo $DIRSTACK[@]
  /sys/class/backlight/intel_backlight /sys/class/backlight/intel_backlight /etc /home/ubuntuadmin
  

  
  


• 
  

  Use symlinks.Example:

  
  
  

  $ ln -s /var/log ~/logs
  $ cd ~/logs
  

  
  
  

  Now instead of doing cd /var/log you can do cd ~/logs. Trivial example, but imagine if /var/log was something like /media/external_harddrive/someproject/subproject/data/bignumbers/calculations/ . We can just do cd ~/calculations then if we have symlink. Of course disadvantage of symlinks is that when directory is renamed or removed, symlink remains and becomes broken, but it's a simple fix - either re-create full path to symlink or remove the symlink and create new one. We can also create a symlink that points to symlink that points to actual directory, but beware that Linux kernel caps too many levels of symlinks ( and you'd get an error that says exactly that) if there are more than 40 symlinks.

  
  
  

  If the goal is to create a fast way of opening the file text.txt the symlink approach can help us with that

  
  
  

  $ echo 'Hello, this is a test' > ~/Documents/another_directory/file.txt
  $ ln -s ~/Documents/another_directory/file.txt ~/file.symlink
  $ cat ~/file.symlink 
  Hello, this is a test
  $ 
  

  
  


• 
  

  You can use inode numbers. This is often used to deal with difficult filenames, where quoting and special characters become a problem. For instance, if we know directory's inode

  
  
  

  # return $HOME
  $ cd
  # find the inode
  $ ls -id ~/Documents/things
  1205421 /home/ubuntuadmin/Documents/things
  # go to the directory by inode
  $ cd "$(find -inum 1205421)"
  $ pwd
  /home/ubuntuadmin/Documents/things
  

  
  
  

  Problem with this approach - it is slow and inefficient, since recursive traversal via find and checking all inodes along the way requires time and a lot of syscalls.