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chapter2/random_file.bash

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+#!/bin/bash
+#
+# SCRIPT: random_file.bash
+# AUTHOR: Randy Michael
+# DATE: 8/3/2007
+# REV: 1.0
+# PLATFORM: Not Platform Dependent
+#
+# PURPOSE: This script is used to create a
+#      specific size file of random characters.
+#      The methods used in this script include
+#      loading an array with alphanumeric 
+#      characters, then using the /dev/random 
+#      character special file to seed the RANDOM
+#      shell variable, which in turn is used to 
+#      extract a random set of characters from the
+#      KEYS array to build the OUTFILE of a 
+#      specified MB size.
+#      
+# set -x # Uncomment to debug this script
+#
+# set -n # Uncomment to check script syntax
+#        # without aby execution. Do not forget
+#        # to put the comment back in or the
+#        # script will never execute.
+#
+##########################################
+# DEFINE FILES AND VARIABLES HERE
+##########################################
+
+typeset -i MB_SIZE=$1
+typeset -i RN
+typeset -i i=1
+typeset -i X=0
+WORKDIR=/scripts
+OUTFILE=${WORKDIR}/largefile.random.txt
+>$OUTFILE
+THIS_SCRIPT=$(basename $0)
+CHAR_FILE=${WORKDIR}/char_file.txt
+
+##########################################
+# DEFINE FUNCTIONS HERE
+##########################################
+
+build_random_line ()
+{
+# This function extracts random characters
+# from the KEYS array by using the RANDOM
+# shell variable
+
+C=1
+LINE=
+until (( C > 79 ))
+do
+   LINE="${LINE}${KEYS[$(($RANDOM % X + 1))]}"
+   (( C = C + 1 ))
+done
+
+# Return the line of random characters
+
+echo "$LINE"
+}
+
+##########################################
+
+elasped_time ()
+{
+SEC=$1
+
+(( SEC < 60 )) && echo -e "[Elasped time: \
+$SEC seconds]\c"
+
+(( SEC >= 60  &&  SEC < 3600 )) && echo -e \
+"[Elasped time: $(( SEC / 60 )) min $(( SEC % 60 )) sec]\c"
+
+(( SEC > 3600 )) && echo -e "[Elasped time: \
+$(( SEC / 3600 )) hr $(( (SEC % 3600) / 60 )) min \
+$(( (SEC % 3600) % 60 )) sec]\c"
+}
+
+##########################################
+
+load_default_keyboard ()
+{
+# Loop through each character in the following list and
+# append each character to the $CHAR_FILE file. This
+# produces a file with one character on each line.
+
+for CHAR in 1 2 3 4 5 6 7 8 9 0 q w e r t y u i o \
+             p a s d f g h j k l  z x c v b n m \
+             Q W E R T Y U I O P A S D F G H J K L \
+             Z X C V B N M 0 1 2 3 4 5 6 7 8 9  
+do
+     echo "$CHAR" >> $CHAR_FILE
+done
+}
+##########################################
+
+usage ()
+{
+echo -e "\nUSAGE: $THIS_SCRIPT Mb_size"
+echo -e "Where Mb_size is the size of the file to build\n"
+}
+ 
+##########################################
+# BEGINNING OF MAIN
+##########################################
+
+if (( $# != 1 ))
+then
+     usage
+     exit 1
+fi
+
+# Test for an integer value
+
+case $MB_SIZE in
+[0-9]) : # Do nothing
+          ;;
+       *) usage
+          ;;
+esac
+
+# Test for the $CHAR_FILE
+
+if [ ! -s "$CHAR_FILE" ]
+then
+     echo -e "\nNOTE: $CHAR_FILE does not esist"
+     echo "Loading default keyboard data."
+     echo -e "Creating $CHAR_FILE...\c"
+     load_default_keyboard
+     echo "Done"
+fi
+
+# Load Character Array
+
+echo -e "\nLoading array with alphanumeric character elements"
+
+while read ARRAY_ELEMENT
+do
+    (( X = X + 1 ))
+    KEYS[$X]=$ARRAY_ELEMENT
+
+done < $CHAR_FILE
+
+echo "Total Array Character Elements: $X"
+
+# Use /dev/random to seed the shell variable RANDOM
+
+echo "Querying the kernel random number generator for a random seed"
+
+RN=$(dd if=/dev/random count=1 2>/dev/null \
+    | od -t u4 | awk '{print $2}'| head -n 1)
+
+# The shell variable RANDOM is limited to 32767
+
+echo "Reducing the random seed value to between 1 and 32767"
+
+RN=$(( RN % 32767 + 1 ))
+
+# Initialize RANDOM with a new seed
+
+echo "Assigning a new seed to the RANDOM shell variable"
+
+RANDOM=$RN
+
+echo "Building a $MB_SIZE MB random character file ==> $OUTFILE"
+echo "Please be patient, this may take some time to complete..."
+echo -e "Executing: .\c"
+
+# Reset the shell SECONDS variable to zero seconds.
+
+SECONDS=0
+
+TOT_LINES=$(( MB_SIZE * 12800 ))
+
+until (( i > TOT_LINES ))
+do
+     build_random_line >> $OUTFILE
+     (( $(( i % 100 )) == 0 )) && echo -e ".\c"
+     (( i = i + 1 ))
+done
+
+# Capture the total seconds
+
+TOT_SEC=$SECONDS
+
+echo -e "\n\nSUCCESS: $OUTFILE created at $MB_SIZE MB\n"
+
+elasped_time $TOT_SEC
+
+# Calculate the bytes/second file creation rate
+
+(( MB_SEC = ( MB_SIZE * 1024000 ) / TOT_SEC ))
+
+echo -e "\n\nFile Creation Rate: $MB_SEC bytes/second\n"
+
+echo -e "File size:\n"
+ls -l $OUTFILE
+echo
+
+##########################################
+# END OF random_file.bash SCRIPT
+##########################################