How can special characters be utilized as variables in sed in a comprehensive manner?

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Special characters can be utilized as variables in sed in a comprehensive manner by using escape characters along with them. Here are some tips to use special characters as variables in sed:

1. Use the $ symbol to access a variable's value. For example, to access the value of the variable var, use $var.

2. Use the \\ symbol to escape special characters like . or *. For example, if a variable val contains a regular expression .*, then use \\.* instead of .* in the sed command.

3. Use single quotes around the sed command to prevent the shell from interpreting any special characters. For example, use 's/'$var'//' instead of "s/$var//".

4. Use double quotes around the variable to allow sed to interpret any backslash escape characters in the variable. For example, use "s/$var/\n/g" to substitute all occurrences of the variable var with a newline character.

5. Use the -e option to execute multiple sed commands in one script. For example, sed -e 's/'$var'//' -e 's/abc/'$val'/' will remove the variable var and replace any occurrence of abc with the value of the variable val.

In summary, using escape characters and proper quoting can allow special characters to be used as variables in sed in a comprehensive manner.