November 18, 2019 in Learning, Tips and Tricks
The navigation keys in less command are similar to Vim editor. In this article, let us look at few less command navigation and other operations which will make you a better command line warrior.
1. Less Command – Search Navigation
Once you’ve opened a log file (or any file) using less file-name, use the following keys to search. Please note that the match will be highlighted automatically by default.
Forward Search
- / – search for a pattern which will take you to the next occurrence.
- n – for next match in forward
- N – for previous match in backward
Backward Search
- ? – search for a pattern which will take you to the previous occurrence.
- n – for next match in backward direction
- N – for previous match in forward direction
Tip: If you dont bother about which direction the search is happening, and you want to search file path, or URL, such as “/home/ramesh/”, you can use backward search (?pattern) which will be handy as you don’t want to escape slashes each time.
Search Path
In forward: /\/home\/aditya\/
In backward: ?/home/aditya/
2. Less Command – Screen Navigation
Use the following screen navigation commands while viewing large log files.
- CTRL+F – forward one window
- CTRL+B – backward one window
- CTRL+D – forward half window
- CTRL+U – backward half window
3. Less Command – Line navigation
In a smaller chunk of data, where you want to locate particular error, you may want to navigate line by line using these keys:
- j – navigate forward by one line
- k – navigate backward by one line
4. Less Command – Other Navigations
The following are other navigation operations that you can use inside the less pager.
- G – go to the end of file
- g – go to the start of file
- q or ZZ – exit the less pager
5. Simulate tail -f inside less pager – Press F
Once you’ve opened a file using less command, any content that is appended to the file after that will not be displayed automatically. However, you can press F less command will show the status ‘waiting for data‘. This is as similar to ‘tail -f’.
6. Less Command – Count magic
Similar to Vim editor navigation command, you can give 10j to scroll 10 lines down, or 10k to go up by 10 lines.
- 10j – 10 lines forward.
- 10k – 10 lines backward.
- CTRL+G – show the current file name along with line, byte and percentage statistics.
7. Other useful Less Command Operations
- v – using the configured editor edit the current file.
- h – summary of less commands
- &pattern – display only the matching lines, not all.
8. Open any types of files using less command
less command can be used to open and view the following 10 different file types:
- PDF File – *.pdf
- Word Document- *.doc
- Image Files – *.gif, *.jpg, *.jpeg, *.png
- TAR Files – *.tar
- TAR Files with gzip – *.tar.gz
- Zip Files – *.zip
- Gzip and Gzip2 Files – *.gz and *.bz2
- ISO Files
- Debian Files – *.deb
- RPM Files – *.rpm
Set the LESSOPEN environment variable to lesspipe
First, make sure the following is set in the environment variable.
$ set | grep less
LESSOPEN='|/usr/bin/lesspipe.sh %s'
Please note that you can also do the following to setup the lesspipe.
$ eval "($lesspipe)"
$ cat ~/.bashrc
eval "($lesspipe)"
- lesspipe, lessfile are the input preprocessor for less, which lets it to open all types of files.
- lesspipe allows you to open while the process of conversion is going on using pipe.
- lessfile completes the conversion first, and then displays the content. This writes the converted thing to a temporary file then displays it.
- You can also write your own input preprocessor, and use it.
File Type 1: How to open a pdf file?
It shows all the text in the pdf file clearly, but ignores the images. The output may have some special characters here and there. But it is definitely readable.
File Type 1: How to open a pdf file?
It shows all the text in the pdf file clearly, but ignores the images. The output may have some special characters here and there. But it is definitely readable.
$ less Linux-101-Hacks.pdf
^LLinux 101 Hacks
www.thegeekstuff.com
o
o
o
Chapter 1: Powerful CD Command Hacks
cd is one of the most frequently used commands during a UNIX session.
The cd command hacks mentioned in this chapter will boost your productivity
File Type 2: How to open a word document file?
$ less pdb.doc
The Python Debugger Pdb
=======================
To use the debugger in its simplest form:
>>> import pdb
>>> pdb.run
The debugger's prompt is Pdb. This will stop in the first
function call in
File Type 3: How to open a jpg, jpeg, png file?
While opening a image file (jpeg, jpg and png), less command shows the following information:
- Name of the file
- Type of file
- Number of pixels — width & height
- Size of the file
$ less testfile.jpeg
testfile.jpeg JPEG 2304x1728 2304x1728+0+0 DirectClass 8-bit 1.57222mb 0.550u 0:02
Note: Similar kind of information will be displayed for other image file types.
9. Less Command – Marked navigation
When you are viewing a large log file using less command, you can mark a particular position and return back to that place again by using that mark.
- ma – mark the current position with the letter ‘a’,
- ‘a – go to the marked position ‘a’.
10. Less Command – Multiple file paging
Method 1: You can open multiple files by passing the file names as arguments.
$ less file1 file2
Method 2: While you are viewing file1, use :e to open the file2 as shown below.
$ less file1
:e file2
Navigation across files: When you opened more than two files ( for e.g – less * ), use the following keys to navigate between files.
- :n – go to the next file.
- :p – go to the previous file.
