#!/bin/sh
#
#   General pattern for testing if a command worked and bailing
#   out if it didn't.

#   NOTE: 'echo' is *not* portable, revise subroutines below when moving
#	  from system to system.

#==============================================================================
#  Subroutines  ===============================================================
#==============================================================================

info ()	# $1 = informational message to STDERR

#  Send an informational message to STDERR

  {
    /bin/echo "% `basename $0`: $1" >&2;
  }

#------------------------------------------------------------------------------

warn ()	# $1 = integer error code;  $2 = message to STDERR

#  Send a warning message to STDERR

  {
    /bin/echo "? `basename $0` ($1): $2" >&2;
  }

#------------------------------------------------------------------------------

die ()	# $1 = integer exit code;  $2 = message to STDERR

#  Send an error message to STDERR and abort script with provided exit code.

  {
    /bin/echo -e "! `basename $0` ($1): $2\n_ $0 script aborted" >&2;
    exit $1;
  }

#==============================================================================
#  Main Line  =================================================================
#==============================================================================


#-------------------------------+
# Test and note if the command	|
# worked or not.		|
#-------------------------------+

    echo "Test 1";
    info "Test 1a";
    if (rm sample.dat)
    then warn $? 'rm sample.dat worked';
    else warn $? 'rm sample.dat failed';
    fi;

    if (rm -f sample.dat)				# rm -f never fails.
    then warn $? 'rm sample.dat worked';
    else warn $? 'rm sample.dat failed';
    fi;


#-------------------------------+
# Single step approaches.	|
# Remember "0" is true and any	|
# other value is false.		|
#-------------------------------+

    echo "Test 2";

	#---------------------------------------+
	# Suceed or die.			|
	#---------------------------------------+

    man man > delete.me || die $? 'unable to create sample input data';


	#---------------------------------------+
	# Null step if OK else error case.	|
	#---------------------------------------+

    if (man man > delete.me)
    then :
    else die $? 'unable to create sample input data';
    fi;


	#---------------------------------------+
	# Capture return code and test for non-	|
	# OK status.				|
	#---------------------------------------+
    
    mv delete.me sample.data;
    exitStat=$?;
    if [ $exitStat -ne 0 ]
    then die $exitStat 'unable to rename file';
    fi;


	#---------------------------------------+
	# Use for-each loop as a block for	|
	# cascading tests, sort of like a DCL	|
	# ON WARNING THEN construct.		|
	#---------------------------------------+

    for blockOK in false; do		# Initially set flag to false.
       man man >delete.me || break;
       mv delete.me sample.dat || break;
       rm sample.dat || break;
       blockOK=true
    done;

    if [ "$blockOK" = "true" ]
    then info 'we made it';
    else die 1 "we didn't make it";
    fi;


#==[ EOF: ok-or-die ]==