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--- bash:quotes [2019/12/07 12:00] – peter
+++ bash:quotes [2020/07/15 09:30] (current) – external edit 127.0.0.1
@@ Line 51: / Line 51: @@
 ----
-===== Concatinating Quotes =====
+==== Escaping Quotes ====
+Putting a **backslash** character **\** in front of a quote removes its special meaning.
+This works inside double quotes, or in the absence of quotes.
+It does not work inside single quotes.
+==== Example ====
+<code bash>
+echo 'Don'\''t walk!'
+echo "Don't walk!"
+echo $'Don\'t talk!'
+</code>
+  * **1st line:**  A single quoted string that can contain anything other than single-quotes.  In this case, an escaped, unquoted single-quote is concatenated with the argument between two single quoted strings.
+  * **2nd line:**  A double-quoted string with all expansions and double-quotes within escaped.
+  * **3rd line:**  A less portable equivalent using $'...':
+**$(...)**-style command substitutions are unique in that the quoting of their contents is completely independent to their surroundings.  This means you don't have to worry about nested quote escaping problems.
+----
+===== Concatenating Quotes =====
 The various types of quotes can be combined, or concatenated, if needed.
@@ Line 106: / Line 130: @@
 ----
+===== Prevent field splitting and ignore glob pattern characters =====
+<code bash>
+cp $file $destination         # WRONG
+cp -- "$file" "$destination"  # Right
+</code>
+In this example, the double quotes protect the value of each parameter from undergoing word splitting or globbing should it happen to contain whitespace or wildcard characters (* or ? or [...]).
+Without the quotes, a filename like hot stuff.mp3 would be split into two words, and each word would be passed to the cp command as a separate argument.  or, a filename that contains * with whitespace around it would produce one word for every file in the current directory.  That is not what we want.
+With the quotes, every character in the value of the filename parameter is treated literally, and the whole value becomes the second argument to the cp command.
+<WRAP info>
+When in doubt, always double-quote your parameter expansions.
+</WRAP>
+----
 ===== Example - using back quotes within single quotes =====