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Tenth Line

Problem Description​

Given a text file file.txt, print just the 10th line of the file.

If the file has less than 10 lines, what should you output? There's no need to output anything (an empty output).

Example​

Example 1:

Assume that `file.txt` has the following content:
Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10

Your script should output the following:
Line 10

Example 2:

Assume that `file.txt` has the following content:
Line 1
Line 2
Line 3

Your script should output nothing since there are less than 10 lines in the file.

Constraints​

  • The file file.txt will have at most 10^3 lines.
  • Each line in the file will have at most 10^3 characters.

Solution Approach​

Approach Overview​

There are multiple ways to achieve this using different shell commands. Here, we demonstrate solutions using sed, awk, and tail with head.

Detailed Steps​

  1. Using sed:

    • The sed command can directly print the 10th line.

  2. Using awk:

    • The awk command can be used to check the line number and print the 10th line.

  3. Using tail and head:

    • The tail command can be used to get the last lines starting from the 10th, and then head can get the first of those lines.

Code Examples​

Shell Script Using sed​

# Using sed to print the 10th line
sed -n '10p' file.txt

Shell Script Using awk​

# Using awk to print the 10th line
awk 'NR == 10' file.txt

Shell Script Using tail and head​

# Using tail and head to print the 10th line
tail -n +10 file.txt | head -n 1

Complexity​

  • Time Complexity: O(n), where n is the number of lines in the file. Each line is read once until the 10th line.

  • Space Complexity: O(1), as no additional space is used beyond the required output.