echo

As we've seen countless times in this book, echo simply prints its arguments to standard output. Now we'll explore the command in greater detail.

Options to echo

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echo accepts a few dash options, listed in Table 7-2.

Table 7-2. echo options

Option

Function

-e

Turns on the interpretation of backslash-escaped characters

-E

Turns off the interpretation of backslash-escaped characters on systems where this mode is the default

-n

Omits the final newline (same as the \c escape sequence)

echo escape sequences

echo accepts a number of escape sequences that start with a backslash.[2] They are listed in Table 7-3.

These sequences exhibit fairly predictable behavior, except for \f: on some displays, it causes a screen clear, while on others it causes a line feed. It ejects the page on most printers. \v is somewhat obsolete; it usually causes a line feed.

Table 7-3. echo escape sequences

Sequence

Character printed

\a

ALERT or CTRL-G (bell)

\b

BACKSPACE or CTRL-H

\c

Omit final NEWLINE

\e

Escape character (same as \E)

\E

Escape character[3]

\f

FORMFEED or CTRL-L

\n

NEWLINE (not at end of command) or CTRL-J

\r

RETURN (ENTER) or CTRL-M

\t

TAB or CTRL-I

\v

VERTICAL TAB or CTRL-K

\ n

ASCII character with octal (base-8) value n, where n is 1 to 3 digits

\0nnn

The eight-bit character whose value is the octal (base-8) value nnn where nnn is 1 to 3 digits

\xHH

The eight-bit character whose value is the hexadecimal (base-16) value HH (one or two digits)

\\

Single backslash

[3] Not available in versions of bash prior to 2.0.

The \n, \0, and \x sequences are even more device-dependent and can be used for complex I/O, such as cursor control and special graphics characters.