Shell Programming and Scripting

#!bin/bash
text="A cat is on a mat."
exp="cat"
newexp="SOMECODEcatSOMECODE"

newtext=${${text}/${exp}/${newexp}}
 == > ERROR "wrong substitution"
newtext=${$text/$exp/$newexp}
 == > ERROR "wrong substitution"
newtext=${"cat is here"/"cat"/"dog"}
 == > newtext is EMPTY STRING - Why not "dog is here" ?

newtext=${text/$exp/$newexp}

$ cat x
#!/bin/bash

# Define terminal escape sequences.
GREEN="\033[1;32m"  # bold, green
NORM="\033[0m"

text="A cat is on a cat mat."  # Added a second "cat"
exp="cat"

# 1 slash matches the first occurance, 2 matches all occurances.
newtext=${text//$exp/$GREEN$exp$NORM}
echo -e "$newtext"

exit 0
$ ./x
A cat is on a cat mat.
$

#!/bin/bash

GREEN="\033[1;32m"
NORM="\033[0m"

text="A cat is on a cat mat."
exp="cat"
newexp="${GREEN}${exp}${NORM}"

newtext=${text//$exp/$newexp}
echo -e "$newtext"

exit 0