ksh/bash Formatting Files through sed by cat file|sed command

Question

I am trying to change the colors of content of a file conditionally. My file is:

A  B  C  D
Value  Value  Value  Value  
Value  Value  Value  Value  
Value  Value  Value  Value  
Value  Value  Value  Value  

My command is cat file4 | sed "s,.*,${esc}[33m&${esc}[0m,", whose logic I understand to be:

1. Cat the file then by sed command edit the contents color by using the ANSI color codes.

But when I run this file generated is not as per desired:

[33mA  B  C  D[0m
[33mValue  Value  Value  Value  [0m
[33mValue  Value  Value  Value  [0m
[33mValue  Value  Value  Value  [0m
[33mValue  Value  Value  Value  [0m

Desired Output:

• Field A should be red.
• Field C should be in blue.
• Field D should be yellow.
• Field B should be green.

Answer 1

Firstly, this is a UUOC (useless use of cat). There is no good eason to use cat here, sed is perfectly able to read files itself, and even if it wasn't, then redirecting standard input from the file would be equivalent to piping it.

esc=$(echo -e '\e')
sed "s,\(.*\)  \(.*\)  \(.*\)  \(.*\),$esc[31m\1  $esc[34m\2  $esc[33m\3  $esc[32m\4$esc[m," file4

This is assuming the two spaces between the fields as you originally specified although that seems to have gone in an edit; adjust accordingly.

I have no idea why you thought your original way (match all text on a line, wrap it between two escape codes (for yellow) would give you multiple colours.