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List:       ast-users
Subject:    Re: [ast-users] ksh echo builtin
From:       David Korn <dgk () research ! att ! com>
Date:       2010-11-15 16:50:51
Message-ID: 201011151650.oAFGoppM029776 () penguin ! research ! att ! com
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Subject: Re: [ast-users] ksh echo builtin
--------


> Hi,
> 
> I've just tested some script, because I've heard some complains that it takes 
> too much time with bash. I did a small benchmark and it was working great.
> bash:  2:49
> zsh:    does not work
> mksh: 1:35
> ksh:    0:35
> 
> unfortunatelly ksh produced wrong output. The problem was with 
> echo -e "\x${VAL}"
> seems ksh echo builtin does not support \xNN. In man page there is:
> > When the first arg does not begin with a -, and none of the arguments 
> > contain a \, then echo prints each of its arguments separated by a space 
> > and terminated by a new-line. Otherwise, the behavior of echo is system
> > dependent and print or printf described below should be used. See 
> > echo(1) for usage and description.
> 
> what does mean "system dependent"? ksh's echo does not behave always the same 
> way?
> 

What the standard means that if you use echo and the first argument is -
or any argument contains a \, you cannot count on what the behavior will be.

ksh93 recognizes -n and -e and treates any other value as operands.
The -n means don't add a new-line.
The -e means emulate system V echo.  The system V echo supported
backslash sequences, but not \Xnn.  It supported octal sequences.

A better bet is to use printf whose behavior is well defined by the
standard.
	printf "\x${VAL}\n"
whould work with all standard shells.

David Korn
dgk@research.att.com
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