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While looking for the plain truth on echo I found this page:
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
It's normally a HTML frame on this site https://pubs.opengroup.org/onlinepubs/9699919799/ (where you can search for "echo").
This claims to be POSIX, but I see no -n and I see \c instead!
What have I found?
GracefulRestart points out that /bin/echo recognises \c but it doesn't do that by default: I must do echo -e for \c to be recognised.
You have found IEEE 1003.1-2017, a.k.a. the Single Unix Specification, published by The Open Group.
For more, see "What exactly is POSIX?", "Difference between POSIX, Single UNIX Specification, and Open Group Base Specifications?", and all of their linked questions and answers.
The -n is there, in boldface no less so it is hard to miss. And yes, \c is standard.
The variations in behaviour of echo are notorious. You should not be surprised that /bin/echo is not the same as a shell built-in echo, and that one requires an -e where another does not. It's not even that simple.
For a long explanation, see "Why is printf better than echo?".
For the little-known variability of printf, ironically involving the very same \c escape sequence, see "Bash printf formating not working".
linux and gnu tools are mostly POSIX compliant, but for a UNIX branding, you need to implement all XSI enhancements. This is where Linux is far from being standard compliant. dash e.g. does not implement support for multibyte characters.
If you were on a POSIX certified platform with UNIX branding, echo did handle \c by default.
This applies to Solaris, AIX, HP-UX and Apple.
Apple even uses bash to support this echo behavior, but you need a specific compile option to make bash compliant by default. This compile option for bash is used for MacOS and for Solaris. So peole may be confused when they realise that bash behaves different on a POSIX certified platform,
Remember: GNU reads GNU is not UNIX.... many GNU tools are not POSIX compliant or not POSIX compliant by default. So be careful when you are not on a certified platform.
BTW: You may get the POSIX branding for small embedded platforms even when you do not support echo \c, but for a UNIX branding, you need to support all XSI extensions to POSIX. Linux does not support most of the XSI extensions. Many Linux distros e.g. use dash as the default shell and dash id definitely not compliant, e.g. because it does not support multi byte characters.
type -a echo. Usually, you will have a shell built-in calledechoprovided by your shell in addition to/usr/bin/echowhich would have the flags you are looking for. The shell built-in usually supersedes the installed program.-nand requires-eto regognise\c$ /bin/echo --versionecho (GNU coreutils) 8.30Copyright (C) 2018 Free Software Foundation, Inc.echo? Since you are mentioning GNU: notes about POSIX compatibility can be found ininfo coreutils echo; they are not included inman echo.If the ‘POSIXLY_CORRECT’ environment variable is set,... I think that answers my question.printfinstead ofecho.