ANSI-C Quoting (Bash Reference Manual)

3.1.2.4 ANSI-C Quoting

Words of the form $'string' are treated specially. The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C standard. Backslash escape sequences, if present, are decoded as follows:\a

alert (bell)\b

backspace\e\E

an escape character (not ANSI C)\f

form feed\n

newline\r

carriage return\t

horizontal tab\v

vertical tab\\

backslash\'

single quote\"

double quote\?

question mark\nnn

the eight-bit character whose value is the octal value nnn (one to three octal digits)\xHH

the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)\uHHHH

the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHH (one to four hex digits)\UHHHHHHHH

the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHHHHHH (one to eight hex digits)\cx

a control-x character

The expanded result is single-quoted, as if the dollar sign had not been present.