Linux modules TryHackMe 

Sed – stream editor 

sed (Stream Editor) ek command-line tool hai jo text ko line by line read karta hai aur us par operation karta hai.

Iska use hota hai:

• Text search karne ke liye
• Word replace karne ke liye
• Lines delete karne ke liye
• Nayi line insert karne ke liye
• Specific line print karne ke liye
• Text formatting ke liye

Yaad rakhiye: Default me sed original file ko change nahi karta. Ye sirf output dikhata hai. Agar file ko permanently edit karna ho to -i option use karte hain.

Syntax- sed [flag][pattern]/[screept] [input file]

             Sed ‘s/john/sajid/’ file.txt

Word Replace (s = substitute)

Yaha par output me john ke jagah sajid dikhayega lekin Original file  me change nahi hua hai .

Original file me change karne ke liye -i use karenge .

Example File

Maan lijiye students.txt file me ye data hai:

Rahul

Amit

Rohit

Rahul

Sajid

sed ‘s/Rahul/Ankit/’ students.txt

Output

Ankit

Amit

Rohit

Rahul

Sajid

Kya hua?

Sirf pehla Rahul replace hua.

Sabhi Rahul Replace Karna

Command

sed ‘s/Rahul/Ankit/g’ students.txt

Output

Ankit

Amit

Rohit

Ankit

Sajid

g ka matlab:

Global (sabhi matches replace karo)

Original File Ko Change Karna

sed -i ‘s/Rahul/Ankit/g’ students.txt

Ab file permanently update ho jayegi.

Line Number Print Karna

Sirf line 3 print karo

sed -n ‘3p’ students.txt

Output

Rohit

Explanation

• -n → default output band only line voise print hoga
• 3p → sirf line 3 print

3,4 number ki line print karne ke liye.

Not -sed command se read kar sakte hai ,edit kar sakte hai aur jitna hame chahiye print kar sakte hai , jo line chahiye wo print kar sakte hai aur last me ager jaruri hua tab ham main file ko update kar sakte hai , jabki ham cat ka bhi use karte aaye hai usme ham file read kar sakte hai , aur nano se file edit kar sakte hai , lekin sed command line aasan aur useful hai .

Range me dekhne ke liye command-

Sed -n ‘2,5p’ students.txt

Last line print karne ke liye command-

sed -n ‘$p’ students.txt

Iska matlab:

• -n → Default output ko band kar deta hai.
• $ → Last line ko represent karta hai.
• p → Print karo.

Agar students.txt me ye data hai:

Rahul

Amit

Rohit

Sajid

Sajid

Output – sajid hoga

Sed -n ‘/rohit/p’ students.txt

Note- rohit jis bhi line me hoga wo line print hoga

2 range ke liye 

Sed -n -e ‘1,2p’ -e ‘4,5p’ students.txt

-e se ek se jyada expresion ke liye