JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD MCA 2022 LINUX PROGRAMMING Previous Question Paper (September/October - 2022 - R17)

To calculate the factorial of a number in a shell script, we can use a loop to multiply the sequence of integers from 1 to the input number.

#!/bin/bash
echo "Enter a number:"
read num
fact=1
for (( i=1; i<=num; i++ ))
do
  fact=$((fact * i))
done
echo "Factorial of $num is $fact"

Input and output redirection allow a shell to change the source of input and the destination of output for commands, moving away from the default standard input (keyboard) and standard output (screen).

Output Redirection: This uses the > operator to overwrite a file with the output of a command, or the >> operator to append output to an existing file. For example, ls > files.txt saves the list of files into files.txt.

Input Redirection: This uses the < operator to take input from a file instead of the keyboard. For example, sort < data.txt reads the contents of data.txt and sorts them.

Additionally, Error Redirection (using 2>) allows capturing error messages separately from standard output, which is useful for logging purposes.