max.sh

Shall高级编程

#!/bin/bash
# max.sh: Maximum of two integers.

E_PARAM_ERR=250    # If less than 2 params passed to function.
EQUAL=251          # Return value if both params equal.
#  Error values out of range of any
#+ params that might be fed to the function.

max2 ()             # Returns larger of two numbers.
{                   # Note: numbers compared must be less than 257.
if [ -z "$2" ]
then
  return $E_PARAM_ERR
fi

if [ "$1" -eq "$2" ]
then
  return $EQUAL
else
  if [ "$1" -gt "$2" ]
  then
    return $1
  else
    return $2
  fi
fi
}

max2 33 34
return_val=$?

if [ "$return_val" -eq $E_PARAM_ERR ]
then
  echo "Need to pass two parameters to the function."
elif [ "$return_val" -eq $EQUAL ]
  then
    echo "The two numbers are equal."
else
    echo "The larger of the two numbers is $return_val."
fi  

  
exit 0

#  Exercise (easy):
#  ---------------
#  Convert this to an interactive script,
#+ that is, have the script ask for input (two numbers).