read stdin in variable howto ?

read stdin in variable howto ?

[Marc Chantreux]

hi all,

is there a way to use $(<) to read stdin ? it will be great for write
something like

for arg ( ${(f)"$(<)"} $@ ) treat_arg $arg

regards
mc

Re: read stdin in variable howto ?

[Marc Chantreux]

> What about using the following:
>    ,-----
>    | while :; do read line; test -n "$line" || break; echo $line; done
>    `-----

for the moment, i use :

typeset stdin
read -d\\0 stdin
logins=( ${(f)stdin})

but it's not as elegant as a ${(f)"$(<)"} would be.

thanks for help
mc

Re: read stdin in variable howto ?

[Artur Penttinen]

>hi all,
>
>is there a way to use $(<) to read stdin ? it will be great for write
>something like
>
>for arg ( ${(f)"$(<)"} $@ ) treat_arg $arg

  # for arg in ${(@f)"$(cat)"}; do print "ARG: $arg"; done
  test pd
  pod
  ^D
  ARG: test pd
  ARG: pod
  #

-- 
wbw, artur

Re: read stdin in variable howto ?

[Marc Chantreux]

le 31/01/2006,
Artur Penttinen nous écrivait :
>   # for arg in ${(@f)"$(cat)"}; do print "ARG: $arg"; done

UUOC ;). i mean : isn't it sad to use cat for that ?

thanks anyway.

regards
mc

Re: read stdin in variable howto ?

[Vincent Lefevre]

On 2006-01-31 10:28:13 +0100, Marc Chantreux wrote:
> is there a way to use $(<) to read stdin ? it will be great for write
> something like
> 
> for arg ( ${(f)"$(<)"} $@ ) treat_arg $arg

$(</dev/stdin) or $(</dev/fd/0)

but I don't know if this is portable.

-- 
Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
Work: CR INRIA - computer arithmetic / SPACES project at LORIA

Re: read stdin in variable howto ?

[Vincent Lefevre]

On 2006-01-31 13:07:44 +0100, Vincent Lefevre wrote:
> On 2006-01-31 10:28:13 +0100, Marc Chantreux wrote:
> > is there a way to use $(<) to read stdin ? it will be great for write
> > something like
> > 
> > for arg ( ${(f)"$(<)"} $@ ) treat_arg $arg
> 
> $(</dev/stdin) or $(</dev/fd/0)
> 
> but I don't know if this is portable.

$(<&0) also works.

-- 
Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
Work: CR INRIA - computer arithmetic / SPACES project at LORIA

Re: read stdin in variable howto ?

[Marc Chantreux]

le 31/01/2006,
Vincent Lefevre nous écrivait :
> $(<&0) also works.

exactly kind of answer i expected! thanks a lot Vincent!

mc

Re: read stdin in variable howto ?

[Stephane Chazelas]

On Tue, Jan 31, 2006 at 02:45:48PM +0100, Marc Chantreux wrote:
> le 31/01/2006,
> Vincent Lefevre nous écrivait :
> > $(<&0) also works.
> 
> exactly kind of answer i expected! thanks a lot Vincent!
[...]

But it does the same thing as $(cat) (it does call cat after a
pipe and a fork through the $NULLCMD mechanism), contrary to $(<
/dev/stdin) which uses the $(< file) special operator.

In $(<&0), it's command substitution, and $NULLCMD <&0. So the
shell forks a "cat" process whose stdout is set to a pipe. the
parent process reads the other end of the pipe to build the
string.

In $(< /dev/stdin), the shell reads the /dev/stdin file by
itself in the current process (no fork, no pipe). /dev/stdin (or
/dev/fd/0 or /proc/self/fd/0) is a special feature of some
operating systems, which on some systems (like Solaris) makes
that an open("/dev/stdin") is equivalent to a dup(0), and on
others (like Linux) opens the same resource as the one pointed
to by the fd 0 of the process (beware that some shells like bash
or ksh have a confusing feature where they emulate that OS
mechanism (well in the Solaris way) (in some circumstancies)).

Note that in both cases, the trailing empty lines are removed.
That's a bug/feature common to all the Bourne like shells.

-- 
Stéphane

Re: read stdin in variable howto ?

[Marc Chantreux]

thanks for detailled explanations, Stephane. Really interesting for me.

regards,
mc