[Perl] Capture system call error message. Post: 302344976

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Top Forums Shell Programming and Scripting [Perl] Capture system call error message. Post 302344976 by ejdv on Tuesday 18th of August 2009 06:25:37 AM

08-18-2009

Registered User

[Perl] Capture system call error message.

Hi,

I googled a bit, but could not find the answer to my problem.
But I am sure it is a common issue.

I have this code:

Code:

#!/bin/perl -w #-d

use strict;

sub remsh_test()
{
my $host = $_[0];

printf "\n----\n\n";

printf "remsh to $host with system call\n";
my $result = system ("remsh $host hostname");
printf "Contents of \$result :\n";
printf "$result\n";

printf "\n----\n\n";

printf "remsh to $host with backticks\n";
$result = `remsh $host hostname`;
printf "Contents of \$result :\n";
printf "$result\n";

printf "\n----\n\n";

printf "remsh to $host with open\n";
open (RESULT, '-|', "remsh $host hostname");
while (<RESULT>) {
        chomp;
        printf "Contents of \$_ :\n";
        printf "$_\n";
        $result = $_;
        printf "Contents of \$result :\n";
        printf "$result\n";
}
close (RESULT);

printf "\n----\n\n";

} # end sub

# === MAIN ===

foreach my $host ("nbsol151", "nbfuz159") {
        &remsh_test($host);
}

The output is following:

Code:

----

remsh to nbsol151 with system call
nbsol151
Contents of $result :
0

----

remsh to nbsol151 with backticks
Contents of $result :
nbsol151


----

remsh to nbsol151 with open
Contents of $_ :
nbsol151
Contents of $result :
nbsol151

----


----

remsh to nbfuz159 with system call
rcmd: nbfuz159: Unknown host
Contents of $result :
256

----

remsh to nbfuz159 with backticks
rcmd: nbfuz159: Unknown host
Contents of $result :


----

remsh to nbfuz159 with open
rcmd: nbfuz159: Unknown host

So the observation is that, when remsh works on the other host, you are able to capture its output and use it in your program.
But when remsh fails, you cannot capture the error and use it in your program.

I am looking for a way to capture this "rcmd: nbfuz159: Unknown host" and to use it in my program.
And I do not want the see "rcmd: nbfuz159: Unknown host" on my screen.

Any thoughts ?

Thanks in advance,

E.J.

ejdv

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ppmtosixel

ppmtosixel(1)						      General Commands Manual						     ppmtosixel(1)

NAME

       ppmtosixel - convert a portable pixmap into DEC sixel format

SYNOPSIS

       ppmtosixel [-raw] [-margin] [ppmfile]

DESCRIPTION

       Reads  a  portable  pixmap  as input.  Produces sixel commands (SIX) as output.	The output is formatted for color printing, e.g. for a DEC
       LJ250 color inkjet printer.

       If RGB values from the PPM file do not have maxval=100, the RGB values are rescaled.  A printer control header and a color assignment table
       begin the SIX file.  Image data is written in a compressed format by default.  A printer control footer ends the image file.

OPTIONS

       -raw   If  specified,  each  pixel  will  be explicitly described in the image file.  If -raw is not specified, output will default to com-
	      pressed format in which identical adjacent pixels are replaced by "repeat pixel" commands.  A raw file is often an order	of  magni-
	      tude larger than a compressed file and prints much slower.

       -margin
	      If  -margin  is not specified, the image will be start at the left margin (of the window, paper, or whatever).  If -margin is speci-
	      fied, a 1.5 inch left margin will offset the image.

PRINTING

       Generally, sixel files must reach the printer unfiltered.  Use the lpr -x option or cat filename > /dev/tty0?.

BUGS

       Upon rescaling, truncation of the least significant bits of RGB values may result in poor color conversion.  If the original PPM maxval was
       greater	than  100,  rescaling  also reduces the image depth.  While the actual RGB values from the ppm file are more or less retained, the
       color palette of the LJ250 may not match the colors on your screen.  This seems to be a printer limitation.

SEE ALSO

       ppm(5)

AUTHOR

       Copyright (C) 1991 by Rick Vinci.

								   26 April 1991						     ppmtosixel(1)