CAT Command

 -- show line numbers of the lines in a file

cat -n <file_name>

creating a file 

cat > testing 

enter content

quite

-- testing file is created

Create a copy of the file

cat StudentData > StudentData

Merging two files and creating a new file.

cat <file1> <file2>  > totaldata.txt

append a content of a file to a existing file

cat <file_name>   >>   <file_name>

showing a file in reverse order  -- cat command now becomes tac

 tac <file_name>

list files 

ls -ltr

list all files in human readable format

ls -ltrh

display files ignoring blank lines

cat -n -b <file_name>

-b // skips blank lines

head command to show only first 10 lines from a file

head <file_name>

first 10 line 

display first 20 lines from a file

head -n 20 <file_name>
or
head -20 <file_name>

display 200 bytes of data from this file

head -c <file_name>

skip last 28 lines 

head -n -28 lines  // the hypen skips the last 28 lines

display 10 lines from the bottom of the file

tail <file_name>

display 20 lines from a file 

tail -n -20 <file_name>

display 2000 bytes from the bottom of the file

tail -c 2000 <file_name>

more command to check page by page

more <file_name> press space to move to the next page

q to checkout of the file

want to display content of the file and also how to use how to use different controls while reading the page

more -d <file_name>  // d flag also instructs you with what control buttons to use 

more command cannot backwards and can move only towards forward direction.

less command can move forward direction and backward direction

less <file_name>

d - for down one page
b - back 
q -- to come back 

grep command

grep -i 2010 <file_name>  > file_name.txt

head -n 12 <file_name> >  file_name.txt

-- Pick 15 lines from the bottom of the file and place it in file named <hotel-search>

tail -n 15 <file_name> >> <filename

Pipe symbol --- pipe symbol can be used to make a link between them

fetching data from the middle of the file 15 - 28

head -n 23 <file_name> | tail -n 8 

the first 23 lines of the file is directed to the another command to fetch last 8 lines from the output given to it using pipe symbol

head -n 23 <file_name> | tail -n 8  | grep 2010

process commands ps -ef -- I want to display only those process that have keyword 'monitor' in them

ps -ef | grep monitor

ls -l | grep -i Folder  // Ignore Case

-i  -- Ignore case












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