Bash Script for Generating All Permutations of a String

This script generates all possible permutations of a given string. It uses recursion to compute the permutations.

Script Explanation

The script defines a function permute that takes two arguments: str (the string to permute) and prefix (the prefix for the permutations). It generates permutations by removing characters one by one and recursively calling itself with the remaining characters.

Script

#!/bin/bash

# Function to generate permutations
permute() {
    local str="$1"
    local prefix="$2"
    
    # If the string is empty, print the permutation
    if [ -z "$str" ]; then
        echo "$prefix"
    else
        # Loop through the string and generate permutations
        for (( i=0; i<${#str}; i++ )); do
            # Extract the character at position i
            local char="${str:$i:1}"
            
            # Form the remaining string
            local remaining="${str:0:i}${str:i+1}"
            
            # Recursive call to permute the remaining string
            permute "$remaining" "$prefix$char"
        done
    fi
}

# Main script
if [ "$#" -ne 1 ]; then
    echo "Usage: $0 "
    exit 1
fi

input_string="$1"
permute "$input_string" ""

How to Run the Script

1. Save the script to a file, for example, permute.sh.

2. Make the script executable: chmod +x permute.sh

3. Run the script with a string argument: ./permute.sh your_string

Example: ./permute.sh abc

Output

The script will print all permutations of the given string to the terminal.

Explanation of the Script

1. Function Definition:
   • permute(): This function takes two arguments:
     • str: The string to permute.
     • prefix: The prefix used to build up permutations.
   • It recursively generates permutations by removing one character at a time from str and adding it to prefix.
2. Base Case:
   • When str is empty, it prints prefix, which is a complete permutation.
3. Recursive Case:
   • For each character in str, it forms a new string (remaining) excluding the current character and recursively calls permute with this new string and the updated prefix.
4. Main Script:
   • Checks if exactly one argument is provided.
   • Calls permute with the input string and an empty prefix.
5. Usage:
   • Save the script, make it executable, and run it with a string to get all permutations.