How to replace an email in a (PHP) file from the command line without sed?

Question

I have a PHP file which contains an email address as with $to = "example-1_2@example-1_2.com"; and I want to replace the email address to another directly from the terminal.

The following code based on another similar code by Kuslanada worked:

read new_email_address
sed -i 's/$to = ".*";$/$to = "'"$new_email_address"'";/' FILE

Kuslananda told me in comments (paraphrasing):

• My expression is the concatenation of a single-quoted string, a double-quoted string (the variable), and then another short single-quoted string

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As a non professional sysadmin I might use sed once in two years and I find its syntax somewhat difficult to remember and confusing for someone like me which doesn't work with it on a regular basis (the quoting rules clued by Kuslananda there are a bit confusing for me, let along when entire sed commands are normally single-quoted by themselves).
Perhaps there is a way to make Kusalananda's command more "intuitive" or "accessible" for some others and myself. Maybe some backslashes to break the command to pieces would help or maybe another utility would be better for me to do such text replacement.

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How to replace an email in a (PHP) file from the command line without sed?

Answer 1

Quoted shell variables will only be expanded if their outer level of quoting is a double quote. To illustrate:

$ var=foo
$ echo '"$var"'
"$var"
$ echo "'$var'"
'foo'

So, variables are only expanded if the outer level of quotes around them is double.

The next problem is that your regular expression is wrong. $ in a regular expression means "the end of the line", so you can't have multiple $ in there like that. I don't really understand what you are trying to do with that regular expression, so I will just assume you want to change the email address found after the string $to =. If so, try this:

sed -i "s/\\$to = \"[^\"]*\"/\\$to = $new_email_address/" FILE

I have to escape the " (\") and $ (\$to) to avoid the $to to be read as a variable and so the inner " don't close the opening ". I also have to add another layer of escape (\\$) so that the $ isn't seen by the shell and is instead passed to sed. And yes, I realize this is ridiculously complicated.

Alternatively, you can separate it into multiple single and double quoted expressions as I think you were trying to do:

sed 's/\$to = "[^"]*"/$to = '"$new_email_address"'/' FILE

Answer 2

You can use the awk utility which looks at lines in terms of fields separated by delimiters you set on the command line with the -F option.

read new_email_address
awk -F '"' -v new="$new_email_address" '
  $1 == "$to = " {$2 = new}
1' OFS='"' your_phpfile

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awk -v q=\" -v new="$new_email_address" '
BEGIN {
  new_esc = new
  gsub(/[&]/, "\\\\&", new_esc)
  repl = q new_esc q";"
}
sub(\
    /\$to = ".*";$/, \
     "$to = " repl   \
)+1' your_phpfile