List File Contents
- head-It displays the beginning of a file.
- tail-It displays the last last part of a file.
- cat-This command is versatile and multi worker.
- tac-Opposite of cat.
- more-Command line diaplays contents in pager form that is either in more format.
- less-Command line diaplays contents in pager form that is either in less format.
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HEAD
- The 'head' command displays the starting content of a file.
- By default, it displays starting 10 lines of any file.
[haritaraka12078@cxln4 ~]$ head jtp.txt
hellllllllllllllllllooooooooooooo
allllllllllllllll
goodmorning
thank you
welcome
software engineer
hari taraka prabhu manyam
you are welcome
linux weindows operating systems
quality engineer
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Head command for multiple files
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If we'll write two file names then it will display first ten lines (in this case file has five lines only) of each file separated by a heading.
[haritaraka12078@cxln4 ~]$ head jtp.txt marks.txt
==> jtp.txt <==
hellllllllllllllllllooooooooooooo
allllllllllllllll
goodmorning
thank you
welcome
software engineer
hari taraka prabhu manyam
you are welcome
linux weindows operating systems
quality engineer
==> marks.txt <==
hellllllllllllllllllooooooooooooo
allllllllllllllll
goodmorning
thank you
welcome
software engineer
hari taraka prabhu manyam
you are welcome
linux weindows operating systems
quality engineer
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head -n
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The 'head -n' option displays specified number of lines.
[haritaraka12078@cxln4 ~]$ head -5 jtp.txt
hellllllllllllllllllooooooooooooo
allllllllllllllll
goodmorning
thank you
welcome
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head -c
The 'head -c' command counts the number of bytes of a file
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[haritaraka12078@cxln4 ~]$ head -c 4 jtp.txt
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TAIL
- Linux tail command is used to display the last ten lines of one or more files. Its main purpose is to read the error message.
[haritaraka12078@cxln4 ~]$ tail jtp.txt
thank you
welcome
software engineer
hari taraka prabhu manyam
you are welcome
linux weindows operating systems
quality engineer
big data hadoop tester
goiod afternoon
happy new year
[haritaraka12078@cxln4 ~]$ tail -n 5 jtp.txt
linux weindows operating systems
quality engineer
big data hadoop tester
goiod afternoon
happy new year
[haritaraka12078@cxln4 ~]$ tail -n 5 jtp.txt marks.txt
==> jtp.txt <==
linux weindows operating systems
quality engineer
big data hadoop tester
goiod afternoon
happy new year
==> marks.txt <==
linux weindows operating systems
quality engineer
big data hadoop tester
goiod afternoon
happy new year
[haritaraka12078@cxln4 ~]$ tail -c 6 marks.txt
year
[haritaraka12078@cxln4 ~]$ tail -f jtp.txt
thank you
welcome
software engineer
hari taraka prabhu manyam
you are welcome
linux weindows operating systems
quality engineer
big data hadoop tester
goiod afternoon
happy new year
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Tail with other commands
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The tail command can be used with other commands. It can be piped to other commands to filter the output. Consider the below command:
[haritaraka12078@cxln4 ~]$ ls -t /etc | tail -n 6
services
mailcap
mime.types
ld.so.conf
rpc
Trolltech.conf
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MORE
- As 'cat' command displays the file content. Same way 'more' command also displays the content of a file.
- Only difference is that, in case of larger files, 'cat' command output will scroll off your screen while 'more' command displays output one screenful at a time.
Following keys are used in 'more' command to scroll the page:
Enter key --------------->> To scroll down page line by line.
Space bar --------------->> To go to next page.
b key --------------->> To go to the backward page.
/ key --------------->> Lets you search the string.
Syntax: more <file name>
- To scroll down use 'space' button, next page will be displayed.
- If you want to scroll down the page line by line use 'enter' key.
- If you want to go to the last or backward page use 'b' key.
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Options Function
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more -num Limits the line displayed per page.
more -d Displays user message at right corner.
more -s Squeeze blank lines.
more +/string name It helps to find the string.
more +num Used to display the content from a specific line.
Note: The 'more' command can't be used to display binary files.
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LESS
- The 'less' command is same as 'more' command but include some more features.
- It automatically adjust with the width and height of the teminal window,
- while 'more' command cuts the content as the width of the terminal window get shorter.
less <file name>
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Linux To Find A String
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A particular string is searched by typing forward slash (/) and then followed by the string name, at place of file name in the lower left corner of the terminal box.
Syntax: /string name
Example: /add
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less Command Navigation Keys
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The 'less' command have navigation keys similar to the 'vim' editor. Let's have a look on some of the navigation keys and other operations of less command.
1. Search Navigation
search navigtion keys will help you in forward and backward search.
Forward search
- / : search for a pattern for the next occurence
- n : search for next match
- N : search for previous match
Backward search
- ? : search for a pattern for the next occurence
- n : for next match in backward direction
- N : for previous match in forward direction
Search path
- Forward : /\/home\/sssit\/
- Backward : /home/sssit
2. Screen Navigation
- Ctrl + f : forwards one window
- Ctrl + d : forwards half window
- Ctrl + b : backwards one window
- Ctrl + u : backwards half window
3. Line Navigation
to move forward or backward line by line
- j : forward by one line
- k : backward by one line
4. other Navigations
- G : used to go to end of the file
- g : used to go to start of the file
- q or ZZ : to exit
5. Count Keys
- 10j : 10 lines forward
- 10k : 10 lines backward
6. Marked Navigation
- ma : mark current position with letter 'a'
- a : go to marked position
7. Multiple File
- by passing arguments in the same line
less file1 file2
- while viewing file1 go to file2
less file1
:e file2
- to navigate between files when more then two files are opened
n : go to next file
p : go to previous file
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CAT
- The 'cat' command is the most universal and powerful tool.
- It is considered to be one of the most frequently used commands.
- It can be used to display the content of a file, copy content from one file to another, concatenate the contents of multiple files, display the line number, display $ at the end of the line, etc.
cat > [fileName] To create a file.
cat [oldfile] > [newfile] To copy content from older to new file.
cat [file1 file2 and so on] > [new file name] To concatenate contents of multiple files into one.
cat -n/cat -b [fileName] To display line numbers.
cat -e [fileName] To display $ character at the end of each line.
cat [fileName] <<EOF Used as page end marker.
ritaraka12078@cxln4 ~]$ cat>exm.txt
apple is red
mango is yellow
your dress color is red
black color suits you all
[haritaraka12078@cxln4 ~]$ cat>>exm.txt
123456789
[haritaraka12078@cxln4 ~]$ cat exm.txt
apple is red
mango is yellow
your dress color is red
black color suits you all
123456789
[haritaraka12078@cxln4 ~]$ cat exm.txt>exm2.txt
[haritaraka12078@cxln4 ~]$ cat exm2.txt
apple is red
mango is yellow
your dress color is red
black color suits you all
123456789
[haritaraka12078@cxln4 ~]$ cat site.txt
sunday monday tuesday wednesday thursday friday saturday
[haritaraka12078@cxln4 ~]$ cat exm.txt site.txt >combo
[haritaraka12078@cxln4 ~]$ cat combo
apple is red
mango is yellow
your dress color is red
black color suits you all
123456789
sunday monday tuesday wednesday thursday friday saturday
[haritaraka12078@cxln4 ~]$ cat - exm.txt site.txt >combo
9874563212356
[haritaraka12078@cxln4 ~]$ cat combo
9874563212356
apple is red
mango is yellow
your dress color is red
black color suits you all
123456789
sunday monday tuesday wednesday thursday friday saturday
[haritaraka12078@cxln4 ~]$ cat -n combo
1 9874563212356
2 apple is red
3 mango is yellow
4 your dress color is red
5 black color suits you all
6 123456789
7 sunday monday tuesday wednesday thursday friday saturday
[haritaraka12078@cxln4 ~]$ cat -b combo
1 9874563212356
2 apple is red
3 mango is yellow
4 your dress color is red
5 black color suits you all
6 123456789
7 sunday monday tuesday wednesday thursday friday saturday
[haritaraka12078@cxln4 ~]$ cat -e exm.txt
apple is red$
mango is yellow$
your dress color is red$
black color suits you all$
123456789$
[haritaraka12078@cxln4 ~]$ cat>exm.txt<<EOF
> apple is red$
> mango is yellow$
> your dress color is red$
> black color suits you all$
> 123456789$
> -bash: warning: here-document at line 141 delimited by end-of-file (wanted `EOF')
[haritaraka12078@cxln4 ~]$ cat weeks.txt | tac | cat | cat | tac
sunday
tuesday
wednesday
saturday
sunday
tuesday
wednesday
saturday
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TAC
- The 'tac' command is the reverse of the 'cat' command.
- It is also known as 'cat' backward. It will display the file content in reverse order.
- It prints the last line first, then second last and so on. Such way, it prints the first line at last.
[haritaraka12078@cxln4 ~]$ cat file2.txt
dhoni
dravid
sachin
zadeja
[haritaraka12078@cxln4 ~]$ tac file2.txt
zadeja
sachin
dravid
dhoni
[haritaraka12078@cxln4 ~]$ tac exm.txt --separator "red"
$
black color suits you all$
123456789$
$
mango is yellow$
your dress color is redapple is red
[haritaraka12078@cxln4 ~]$ tac exm.txt --separator "yellow"
$
your dress color is red$
black color suits you all$
123456789$
apple is red$
mango is yellow
tac exm.txt --separator "all"
$
123456789$
apple is red$
mango is yellow$
your dress color is red$
black color suits you all [haritaraka12078@cxln4 ~]$
