14

I dump a string with hexdump like this 2031 3334 2e30 0a32 2032 3331 302e 000a. It is clear that 0x0a is new line character, however, when I try to echo this string out, I always got 1 430.2 2 13.0 -- the new line is replaced with a space, even I use the -e flag.

What may be the problem? Does the tailing \0 ruin the output? Is there any alternatives to print 0x0a a new line?

Thanks and Best regards.

23

The new line character with the echo command is "\n". Taking the following example:

echo -e "This is line 1\nThis is line 2"

Would result in the output

This is line 1
This is line 2

The "-e" parameter is important here.

  • 3
    btw, this "echo -e ..." relies on bash's echo to work correctly (e.g., dash will just print the "-e"); but '/bin/echo' may (or may not) also work. Unfortunately (perhaps appropriately), there are a lot of echo's around, and you don't really want to care about which one you're going to get. Using 'printf "....\n" is a more portable option across env's and shells. – michael May 3 '15 at 8:03
  • @michael_n which is what the OP finally reverted too, in fact. But the question was explicitely stating "with echo" – hence my answer this way. Anyhow, it was not "with Bash" – so thanks for your pointing out those differences! – Izzy May 4 '15 at 9:28
4

POSIX 7 says you can't

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html

-e is not defined and backslashes are implementation defined:

If the first operand is -n, or if any of the operands contain a <backslash> character, the results are implementation-defined.

unless you have an optional XSI extension.

So use printf instead:

format operand shall be used as the format string described in XBD File Format Notation [...]

the File Format Notation:

\n <newline> Move the printing position to the start of the next line.

Also keep in mind that Ubuntu 15.10 and most distros implement echo both as:

  • a Bash built-in: help echo
  • a standalone executable: which echo

which can lead to some confusion.

2

I finally properly format this string with printf "$string". Thank you all.

  • What is this $string that you speak of? How is this connected to the question? What is does it not involve \n as in the other two answers? – Peter Mortensen Apr 15 at 0:08

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