Sed_command-4.sh

# Sed is a popular utility which enables quick parsing and transformation of text.

# Here are some very simple examples of sed in action.

# Substitute the first occurrence of 'editor' with 'tool'.

# `$:~/hackerrank/bash/grep/grep1$` echo "My favorite programming editor is Emacs. Another editor I like is Vim." | sed -e s/editor/tool/
# My favorite programming tool is Emacs. Another editor I like is Vim.
# Substitute all the occurrences of 'editor' with 'tool'.

# `$:~/hackerrank/bash/grep/grep1$` echo "My favorite programming editor is Emacs. Another editor I like is Vim." | sed -e s/editor/tool/g
# My favorite programming tool is Emacs. Another tool I like is Vim.  
# Substitute the second occurrence of 'editor' with 'tool'.

# `$:~/hackerrank/bash/grep/grep1$` echo "My favorite programming editor is Emacs. Another editor I like is Vim." | sed -e s/editor/tool/2
# My favorite programming editor is Emacs. Another tool I like is Vim.
# Highlight all the occurrences of 'editor' by wrapping them up in brace brackets.

# `$:~/hackerrank/bash/grep/grep1$` echo "My favorite programming editor is Emacs. Another editor I like is Vim." | sed -e s/editor/{\&}/g
# My favorite programming {editor} is Emacs. Another {editor} I like is Vim.
# Some references for learning about sed have been included:
# Sed - An Introduction and a tutorial
# The TLDP Guide
# Some Practical Examples

# Task

# Given an input file, with N credit card numbers, each in a new line, your task is to reverse the ordering of segments in each credit card number. Assume that the credit card numbers will have 4 space separated segments with 4 digits each.

# If the original credit card number is 1434 5678 9101 1234, transform it to 1234 9101 5678 1434.

# Useful References: This particular page on StackOverflow has a relevant example about sed, groups and backreferences. Here's a detailed tutorial covering groups and backreferences.

# Input Format

# N credit card numbers, each in a new line, credit card numbers will have 4 space separated segments with 4 digits each.

# Constraints
#1<=N<=20

# However, the value of N does not matter while writing your command.

# Output Format

# N lines, each containing a credit card number with the ordering of its segments reversed.

# Sample Input

# 1234 5678 9101 1234  
# 2999 5178 9101 2234  
# 9999 5628 9201 1232  
# 8888 3678 9101 1232
# Sample Output

# 1234 9101 5678 1234  
# 2234 9101 5178 2999  
# 1232 9201 5628 9999  
# 1232 9101 3678 8888 
# Explanation

# The order of the four segments in the (input) credit card numbers have been reversed.