tangetools/neno/neno

#!/bin/bash

: <<=cut
=pod

=head1 NAME

neno - no error no output


=head1 SYNOPSIS

B<neno> I<command1> [\; I<command2> ...]


=head1 DESCRIPTION

B<neno> will print the output from both standard output and standard
error if the composed command returns an error. If the composed
command returns true, the output will be ignored.  This is useful for
cron jobs where you only want output if it failed.


=head1 EXAMPLE

Give output for missing file:

  neno ls /missing-file

No output if file exists:

  neno ls /bin/sh


=head1 AUTHOR

Copyright (C) 2017 Ole Tange,
http://ole.tange.dk and Free Software Foundation, Inc.


=head1 LICENSE

Copyright (C) 2012 Free Software Foundation, Inc.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
at your option any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.


=head1 SEE ALSO

B<man>


=cut

print() {
  cat $TMP/stdout >&3
  cat $TMP/stderr >&4
}

cleanup() {
  rm -rf $TMP
  return $?
}
 
control_c() {
  # Run if user hits control-C
  # >&4 is the non-redirected stderr
  echo >&4
  print
  echo -en "\n$0: CTRL-C hit: Exiting.\n" >&4
  cleanup
  exit $?
}
 
# trap keyboard interrupt (control-c)
trap control_c SIGINT

TMP=$(mktemp -d /tmp/no-error.XXXXX)
exec 3>&1 4>&2
eval $* 2>$TMP/stderr >$TMP/stdout
ERROR=$?
if [ $ERROR == 0 ] ; then
  # skip
  true
else
  print
fi
cleanup
exit $ERROR