printf newline

printf newline

[Johan DS]

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hi
does anybody has a clou why if I:
$ printf texta \n textb

The output is:

texta%

and not:
texta
textb

Thanks

Re: printf newline

[Peter Stephenson]

On Sun, 6 Nov 2016 18:29:44 +0100
Johan DS <victor3xray@gmail.com> wrote:
> hi
> does anybody has a clou why if I:
> $ printf texta \n textb
> 
> The output is:
> 
> texta%
> 
> and not:
> texta
> textb

(I presume you've missed out some quotes?  In what you show the
backslash would be swallowed up when reading the command line and so
you'd get an "n" rather than a newline.)

There's no implicit newline at the end of printf output, unlike print.
Because the shell needs to know where it is on the terminal (as zsh
handles multiple lines on the screen, unlike most other command line
environments), it goes back to the beginning of the line, swallowing up
the textb.

If you really need, you can "unsetopt prompt_cr", but you're liable to
see side effects.  For most of us it's usually more convenient just to
add the extra newlines.

pws

Re: printf newline

[Daniel Shahaf]

Peter Stephenson wrote on Mon, Nov 07, 2016 at 09:46:29 +0000:
> On Sun, 6 Nov 2016 18:29:44 +0100
> Johan DS <victor3xray@gmail.com> wrote:
> > hi
> > does anybody has a clou why if I:
> > $ printf texta \n textb
> > 
> > The output is:
> > 
> > texta%
> > 
> > and not:
> > texta
> > textb
> 
> (I presume you've missed out some quotes?  In what you show the
> backslash would be swallowed up when reading the command line and so
> you'd get an "n" rather than a newline.)
> 

I think the question was, why the \n and the textb weren't used.

The answer is that printf's interface is different from echo's.  printf
interprets its first argument as a format string that describes how to
use the remaining arguments.  The format string "texta" instructs to
print "texta" and to ignore any further arguments.  The "%" is then
generated by the PROMPT_* options.

For the \n to be interpreted by printf, it must be in the first
argument.  Adding the details Peter described gives:

    printf 'texta\ntextb\n'

which would do what you want.

Cheers,

Daniel

> There's no implicit newline at the end of printf output, unlike print.
> Because the shell needs to know where it is on the terminal (as zsh
> handles multiple lines on the screen, unlike most other command line
> environments), it goes back to the beginning of the line, swallowing up
> the textb.
> 
> If you really need, you can "unsetopt prompt_cr", but you're liable to
> see side effects.  For most of us it's usually more convenient just to
> add the extra newlines.
> 
> pws
>