Re: Printing "-n" with the echo command

[email protected] wrote:
> We use the command "echo" in program building scripts.

You are probably using the shell built-in echo in that case.  Which
shell are you using for your scripts?  Hopefully #!/bin/sh but which
shell is that on your system?  The possibilities are many and include
ash, bash, ksh, old bourne shell, or a native POSIX shell
implementation such as on some commercial systems.  On my system I can
do the following and see that it is a shell builtin.

  type echo
  echo is a shell builtin

> When echoing build
> parameters as "-n" alone, the characters "-n" are never echoed and by the
> way are lost.
> Ex.
> > TOTO="-n"
> > echo "$TOTO"
> > echo "-n"
> > echo "-n -a"
> -n -a

Since I am looking at bash's built-in version I can use its online
help system.

  help echo
  echo: echo [-neE] [arg ...]
      Output the ARGs.  If -n is specified, the trailing newline is
      suppressed.

But that is not portable.  Better to use 'printf' instead.

If I recall correctly at one time System V systems (known as USG echo)
always interpreted escape sequences such as \c for don't print a
newline and never used the -n -e options.  BSD systems on the other
hand wrote a different echo command which did not interpret escape
sequences without -e and used -n to avoid printing the newline.  Ack!
Why couldn't they have converged years ago to a common standard?  So
the flavor of command you like depends on whether you want the SysV
flavor or the BSD flavor.  POSIX specifies the SysV behavior but most
Linux distributions go with the bash default and the bash default is
BSD behavior in violation of the standard.  Meanwhile FreeBSD at least
is now using a POSIX standard shell so BSD-like is no longer a good
description since BSD today is POSIX in this regard.  This is all off
of the top of my head and I probably have ten details wrong, sorry,
but you can see the flamefest that you have stepped into by this.
That was all that I intended by this paragraph.

> I understand "-n" is an option of the "echo" command, but could it be
> possible to print it as regular text when placed between quotes ?

If you want to print a literal -n at the front of the string then it
is better to use printf instead.  This problem with echo has been
around for years and I would not expect it to be cleared up any time
soon.

  printf -- "-n\n"

Quotes are processed by the shell.  Commands invoked from the shell do
not see any quotes.  So the answer is no that does not work.

You could write a new shell that did a different style of quoting.
But that would be a lot of work and would be completely different than
anyone else.  So it is better to understand shell quoting.

> PS.  We use the shell command "echo" of the RedHat V7.3 distribution

In that case the 'echo' you are experiencing is from bash-2.05a or
very close to that version.  I could not really say since I am using
Debian GNU/Linux myself.  Since different people use different
distributions of the same software it is always best to state the
version of the software you are talking about rather than who
distributed it.  Saying Red Hat 7.3 means nothing in this context,
especially to someone who does not have that particular variant around
to go look.  But saying bash-2.05a means exactly a particular version
which anyone can know on many different systems.

You can usually get the version from commands by asking the command
with the --version option such as here.

  bash --version
  GNU bash, version 2.05b.0(1)-release (i386-pc-linux-gnu)

I say usually because the built-in echo does not work this way.  But
the echo supplied with coreutils does.
  
  echo --version
  --version

  /bin/echo --version
  echo (GNU coreutils) 5.0.91

  [coreutils is the newer version of sh-utils and also includes
  fileutils and textutils.]

So thank you for reporting the problem.  But as you can see we over
here are the /bin/echo folks and not the shell built-in folks.  But
also as you can see they do behave the same so it did not matter.  But
you are stuck.  Use printf instead.

Bob