substitution

This question already has an answer here: How to cat <<EOF >> a file containing code? 3 answers I'm trying to create a script file using substitution string from ENV but want also to prevent some from escaping export PLACEHOLDER1="myPlaceholder1Value" export PLACEHOLDER2="myPlaceholder2Value" sudo /bin/su -c "cat << EOF > /etc/init.d/my-script #!/bin/bash # ### BEGIN INIT INFO # Provides: my-script # Required-Start: \$remote_fs \$syslog # Required-Stop: \$remote_fs \$syslog # Should-Start: \$network \$time # Should-Stop: \$network \$time # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short

I would like to do the following: $find="start (.*) end"; $replace="foo \1 bar"; $var = "start middle end"; $var =~ s/$find/$replace/; I would expect $var to contain "foo middle bar", but it does not work. Neither does: $replace='foo \1 bar'; Somehow I am missing something regarding the escaping. I fixed the missing 's' On the replacement side, you must use $1, not \1. And you can only do what you want by making replace an evalable expression that gives the result you want and telling s/// to eval it with the /ee modifier like so: $find="start (.*) end"; $replace='"foo $1 bar"'; $var = "start

This question already has an answer here: What is the difference between $(command) and `command` in shell programming? 6 answers What's the preferred way to do command substitution in bash? I've always done it like this: echo "Hello, `whoami`." But recently, I've often seen it written like this: echo "Hello, $(whoami)." What's the preferred syntax, and why? Or are they pretty much interchangeable? I tend to favor the first, simply because my text editor seems to know what it is, and does syntax highlighting appropriately. I read here that escaped characters act a bit differently in each case,