Head Command: -

Q) What is head command ?

Ans – Head command will show 1^st ten lines of a file.

Q) How you will see 1^st 10 lines of a file ?

Ans - $ head <File Name><Enter – Key>

Example - $ head f1.txt

Q) How you will see 1^st 15 lines of a file ?

Ans - $ head -15 <File Name><Enter – Key>

Q) How you will see 1^st 30 lines of both the files file1.txt and file2.txt ?

Ans - $ head -30 file1.txt file2.txt<Enter – Key>

Here you will get 1^st 30 lines of both the files with a header file name before each file records.

Tail Command: -

Q) What is tail command ?

Ans – Tail command will show last ten lines of a file.

Q) How you will see last 10 lines of a file ?

Ans - $ tail <File Name><Enter – Key>

Example - $ tail f1.txt

Q) How you will see last 15 lines of a file ?

Ans - $ tail -15 <File Name><Enter – Key>

Q) How you will see log file error message ?

Ans - $ tail –f <Log File Name> | grep error<Enter – Key>

| -> Pipe Operator

Grep -> This command is used to find all the pattern error present inside the log file.

More Command: -

Q) What is more command ?

Ans – more command is used to see the file content in page wise from top to bottom.

Example - $ more file.txt<Enter – Key>

Here you will find the 1^st page. Then by clicking space bar, you will move to next page.

Q) How you will exit from more command or from the file content ?

Ans – By clicking ‘Q’ (Capital Q)

Q) How is more command is useful ?

Ans – more command search pattern in forward direction, not in backward direction.

After you open any file by help of more command, then you need to press ‘/’ (Forward Slash) and then space and then pattern. You will find the pattern, then by hitting ‘n’ you will move to next occurrence of the pattern.

Less Command: -

Q) What is less command ?

Ans – less command is used to see the file content in page wise from bottom.

Example - $ less file.txt<Enter – Key>

Here you will find the last page.

Q) How you will exit from less command or from the file content ?

Ans – By clicking ‘Q’ (Capital Q)

Q) How is less command is useful ?

Ans – less command searches pattern in forward and backward direction.

After you open any file by help of less command, then you need to press ‘/’ (Forward Slash) and then space and then pattern. You will find the pattern, then by hitting ‘n’ you will move to next occurrence of the pattern and ‘shift + n’ you will move to previous pattern.

Absolute Path and Relative Path: -

Q) What is absolute path ?

Ans - An absolute path is defined as specifying the location of a file or directory from the root directory(/).

Q) What is Relative Path ?

Ans - Relative path is defined as the path related to the present working directory(pwd). Relative Path never begins with ‘/’ (Root Directory).

PIPE (|): -

Q) What is pipe operator (|) ?

Ans – pipe operator is used to combine multiple commands at a time to get a single desired output.

Q) How to find an ip address 101.21.3.41 present in the log file f1.log or not ?

Ans – tail –f f1.log | grep 101.21.3.41<Enter – Key>

Q) How to see 15^th to 27^th lines present inside the file file.dat ?

Ans - $ head -27 file.dat | tail -13<Enter – Key>

Q) How to see 34^th line of a file f1?

Ans - $ head -34 f1 | tail -1<Enter – Key>

Q) Store 1^st 30 lines of a file file.csv into a file f1 ?

Ans - $ head -30 file.csv > f1<Enter – Key>

Q) Append 30^th to 45^th lines of a file file.log into a file f2 ?

Ans - $ head -45 file.log | tail -16 >> f2<Enter – Key>