Category: Unix

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.
-i - ignore case in searches
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\/ramesh\/
In backward: ?/home/ramesh/

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’.

Also, refer to our earlier article about how to view multiple logs files using 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

As we discussed in our earlier article, you can use less command to Open & view 10 different 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.