New helper ynh_replace_string (#280)

* New helper ynh_substitute_char
Sed abstraction, and a way to use something other than sed.
I added also an escape of the delimiter used by sed, to prevent a fail in this case.
* Renaming to ynh_replace_string
* Renaming variable for clarity

data/helpers.d/string

@@ -9,3 +9,18 @@ ynh_string_random() {
       | tr -c -d 'A-Za-z0-9' \
       | sed -n 's/\(.\{'"${1:-24}"'\}\).*/\1/p'
 }
+
+# Substitute/replace a string by another in a file
+#
+# usage: ynh_replace_string match_string replace_string target_file
+# | arg: match_string - String to be searched and replaced in the file
+# | arg: replace_string - String that will replace matches
+# | arg: target_file - File in which the string will be replaced.
+ynh_replace_string () {
+	delimit=@
+	match_string=${1//${delimit}/"\\${delimit}"}	# Escape the delimiter if it's in the string.
+	replace_string=${2//${delimit}/"\\${delimit}"}
+	workfile=$3
+
+	sudo sed --in-place "s${delimit}${match_string}${delimit}${replace_string}${delimit}g" "$workfile"
+}