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chapter11/mk_unique_filename.ksh

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+#!/usr/bin/ksh
+#
+# AUTHOR: Randy Micahel
+# SCRIPT: mk_unique_filename.ksh
+# DATE: 11/12/2007
+# REV: 1.2.P
+#
+# PLATFORM: Not Platform Dependent
+#
+# EXIT CODES:
+#               0 - Normal script execution
+#               1 - Usage error
+#
+# REV LIST:
+#
+#
+# set -x # Uncomment to debug
+# set -n # Uncomment to debug without any execution
+#
+####################################################
+########## DEFINE FUNCTIONS HERE ###################
+####################################################
+
+function usage
+{
+echo "\nUSAGE: $SCRIPT_NAME base_file_name\n"
+}
+
+####################################################
+
+function get_date_time_stamp
+{
+DATE_STAMP=$(date +'%m%d%y.%H%M%S')
+echo $DATE_STAMP
+}
+
+####################################################
+
+function get_second
+{
+THIS_SECOND=$(date +%S)
+echo $THIS_SECOND
+}
+
+####################################################
+
+function in_range_fixed_length_random_number_typeset
+{
+# Create a pseudo-random number less than or equal
+# to the $UPPER_LIMIT value, which is user defined.
+# This function will also pad the output with leading
+# zeros to keep the number of digits consistent using
+# the typeset command.
+
+# Find the length of each character string
+
+UL_LENGTH=$(echo ${#UPPER_LIMIT})
+
+# Fix the length of the RANDOM_NUMBER variable to
+# the length of the UPPER_LIMIT variable, specified
+# by the $UL_LENGTH variable.
+
+typeset -Z$UL_LENGTH RANDOM_NUMBER
+
+# Create a fixed length pseudo-random number
+
+RANDOM_NUMBER=$(($RANDOM % $UPPER_LIMIT + 1))
+
+# Return the value of the fixed length $RANDOM_NUMBER
+
+echo $RANDOM_NUMBER
+}
+
+####################################################
+
+function my_program
+{
+# Put anything you want to process in this function. I
+# recommend that you specify an external program of shell
+# script to execute.
+
+echo "HELLO WORLD - $DATE_ST" > $UNIQUE_FN &
+
+#    :  # No-Op - Does nothing but has a return code of zero
+}
+
+####################################################
+################ BEGINNING OF MAIN #################
+####################################################
+
+SCRIPT_NAME=$(basename $0) # Query the system for this script name
+
+# Check for the correct number of arguments - exactly 1
+
+if (( $# != 1 ))
+then
+      echo "\nERROR: Usage error...EXITING..."
+      usage
+      exit 1
+fi
+
+# What filename do we need to make unique?
+
+BASE_FN=$1    # Get the BASE filenaname to make unique
+
+RANDOM=$$      # Initialize the RANDOM environment variable
+               # with the current process ID (PID)
+
+UPPER_LIMIT=32767 # Set the UPPER_LIMIT
+
+CURRENT_SECOND=99 # Initialize to a non-second
+LAST_SECOND=98    # Initialize to a non-second
+
+USED_NUMBERS=     # Initialize to null
+
+PROCESSING="TRUE" # Initialize to run mode
+
+while [[ $PROCESSING = "TRUE" ]]
+do
+     DATE_ST=$(get_date_time_stamp) # Get the current date/time
+     CURRENT_SECOND=$(get_second)   # Get the current second
+
+     RN=$(in_range_fixed_length_random_number_typeset) # Get a new number
+
+     # Check to see if we have already used this number this second
+
+     if (( CURRENT_SECOND == LAST_SECOND ))
+     then
+          UNIQUE=FALSE # Initialize to FALSE
+          while [[ "$UNIQUE" != "TRUE" ]] && [[ ! -z $UNIQUE ]]
+          do
+             # Has this number already been used this second?
+             echo $USED_NUMBERS | grep $RN >/dev/null 2>&1
+             if (( $? == 0 ))
+             then
+                 # Has been used...Get another number
+                 RN=$(in_range_fixed_length_random_number_typeset)
+             else
+                 # Number is unique this second...
+                 UNIQUE=TRUE
+                 # Add this numner to the used number list
+                 USED_NUMBERS="$USED_NUMBERS $RN"
+             fi
+          done
+     else
+          USED_NUMBERS=   # New second...Reinitialize to null
+     fi
+     # Assign the unique filename to the UNIQUE_FN variable
+
+     UNIQUE_FN=${BASE_FN}.${DATE_ST}.$RN
+
+     echo $UNIQUE_FN # Comment out this line!!
+
+     LAST_SECOND=$CURRENT_SECOND # Save the last second value
+
+     # We have a unique filename...
+     #
+     # PROCESS SOMETHING HERE AND REDIRECT OUTPUT TO $UNIQUE_FN
+     #
+     my_program
+     #
+     # IF PROCESSING IS FINISHED ASSIGN "FALSE" to the PROCESSING VARIABLE
+     #
+     # if [[ $MY_PROCESS = "done" ]]
+     # then
+     #      PROCESSING="FALSE"
+     # fi
+done