mirror of https://github.com/tLDP/LDP
add missing
This commit is contained in:
gferg
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#!/bin/bash
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# blotout.sh: Erase all traces of a file.
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# This script overwrites a target file alternately
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#+ with random bytes, then zeros before finally deleting it.
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# After that, even examining the raw disk sectors
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#+ will not reveal the original file data.
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PASSES=7 # Number of file-shredding passes.
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BLOCKSIZE=1 # I/O with /dev/urandom requires unit block size,
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#+ otherwise you get weird results.
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E_BADARGS=70
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E_NOT_FOUND=71
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E_CHANGED_MIND=72
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if [ -z "$1" ] # No filename specified.
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then
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echo "Usage: `basename $0` filename"
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exit $E_BADARGS
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fi
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file=$1
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if [ ! -e "$file" ]
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then
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echo "File \"$file\" not found."
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exit $E_NOT_FOUND
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fi
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echo; echo -n "Are you absolutely sure you want to blot out \"$file\" (y/n)? "
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read answer
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case "$answer" in
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[nN]) echo "Changed your mind, huh?"
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exit $E_CHANGED_MIND
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;;
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*) echo "Blotting out file \"$file\".";;
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esac
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flength=$(ls -l "$file" | awk '{print $5}') # Field 5 is file length.
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pass_count=1
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echo
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while [ "$pass_count" -le "$PASSES" ]
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do
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echo "Pass #$pass_count"
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sync # Flush buffers.
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dd if=/dev/urandom of=$file bs=$BLOCKSIZE count=$flength
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# Fill with random bytes.
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sync # Flush buffers again.
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dd if=/dev/zero of=$file bs=$BLOCKSIZE count=$flength
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# Fill with zeros.
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sync # Flush buffers yet again.
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let "pass_count += 1"
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echo
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done
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rm -f $file # Finally, delete scrambled and shredded file.
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sync # Flush buffers a final time.
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echo "File \"$file\" blotted out and deleted."; echo
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# This is a fairly secure, if inefficient and slow method
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#+ of thoroughly "shredding" a file.
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# The file cannot not be "undeleted" or retrieved by normal methods.
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# However...
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#+ this simple method will likely *not* withstand forensic analysis.
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# Tom Vier's "wipe" file-deletion package does a much more thorough job
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#+ of file shredding than this simple script.
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# http://www.ibiblio.org/pub/Linux/utils/file/wipe-2.0.0.tar.bz2
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# For an in-depth analysis on the topic of file deletion and security,
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#+ see Peter Gutmann's paper,
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#+ "Secure Deletion of Data From Magnetic and Solid-State Memory".
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# http://www.cs.auckland.ac.nz/~pgut001/secure_del.html
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exit 0
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#!/bin/bash
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# crypto-quote.sh: Encrypt quotes
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# Will encrypt famous quotes in a simple monoalphabetic substitution.
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# The result is similar to the "Crypto Quote" puzzles
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# seen in the Op Ed pages of the Sunday paper.
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key=ETAOINSHRDLUBCFGJMQPVWZYXK
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# The "key" is nothing more than a scrambled alphabet.
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# Changing the "key" changes the encryption.
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# The 'cat "$@"' construction gets input either from stdin or from files.
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# If using stdin, terminate input with a Control-D.
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# Otherwise, specify filename as command-line parameter.
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cat "$@" | tr "a-z" "A-Z" | tr "A-Z" "$key"
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# | to uppercase | encrypt
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# Will work on lowercase, uppercase, or mixed-case quotes.
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# Passes non-alphabetic characters through unchanged.
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# Try this script with something like
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# "Nothing so needs reforming as other people's habits."
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# --Mark Twain
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#
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# Output is:
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# "CFPHRCS QF CIIOQ MINFMBRCS EQ FPHIM GIFGUI'Q HETRPQ."
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# --BEML PZERC
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# To reverse the encryption:
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# cat "$@" | tr "$key" "A-Z"
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# This simple-minded cipher can be broken by an average 12-year old
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# using only pencil and paper.
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exit 0
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#!/bin/bash
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# days-between.sh: Number of days between two dates.
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# Usage: ./days-between.sh [M]M/[D]D/YYYY [M]M/[D]D/YYYY
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ARGS=2 # Two command line parameters expected.
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E_PARAM_ERR=65 # Param error.
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REFYR=1600 # Reference year.
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CENTURY=100
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DIY=365
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ADJ_DIY=367 # Adjusted for leap year + fraction.
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MIY=12
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DIM=31
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LEAPCYCLE=4
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MAXRETVAL=256 # Largest permissable
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# positive return value from a function.
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diff= # Declare global variable for date difference.
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value= # Declare global variable for absolute value.
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day= # Declare globals for day, month, year.
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month=
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year=
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Param_Error () # Command line parameters wrong.
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{
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echo "Usage: `basename $0` [M]M/[D]D/YYYY [M]M/[D]D/YYYY"
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echo " (date must be after 1/3/1600)"
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exit $E_PARAM_ERR
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}
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Parse_Date () # Parse date from command line params.
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{
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month=${1%%/**}
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dm=${1%/**} # Day and month.
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day=${dm#*/}
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let "year = `basename $1`" # Not a filename, but works just the same.
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}
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check_date () # Checks for invalid date(s) passed.
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{
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[ "$day" -gt "$DIM" ] || [ "$month" -gt "$MIY" ] || [ "$year" -lt "$REFYR" ] && Param_Error
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# Exit script on bad value(s).
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# Uses "or-list / and-list".
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# Exercise for the reader: Implement more rigorous date checking.
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}
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strip_leading_zero () # Better to strip possible leading zero(s)
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{ # from day and/or month
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val=${1#0} # since otherwise Bash will interpret them
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return $val # as octal values (POSIX.2, sect 2.9.2.1).
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}
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day_index () # Gauss' Formula:
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{ # Days from Jan. 3, 1600 to date passed as param.
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day=$1
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month=$2
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year=$3
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let "month = $month - 2"
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if [ "$month" -le 0 ]
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then
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let "month += 12"
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let "year -= 1"
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fi
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let "year -= $REFYR"
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let "indexyr = $year / $CENTURY"
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let "Days = $DIY*$year + $year/$LEAPCYCLE - $indexyr + $indexyr/$LEAPCYCLE + $ADJ_DIY*$month/$MIY + $day - $DIM"
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# For an in-depth explanation of this algorithm, see
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# http://home.t-online.de/home/berndt.schwerdtfeger/cal.htm
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if [ "$Days" -gt "$MAXRETVAL" ] # If greater than 256,
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then # then change to negative value
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let "dindex = 0 - $Days" # which can be returned from function.
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else let "dindex = $Days"
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fi
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return $dindex
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}
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calculate_difference () # Difference between to day indices.
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{
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let "diff = $1 - $2" # Global variable.
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}
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abs () # Absolute value
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{ # Uses global "value" variable.
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if [ "$1" -lt 0 ] # If negative
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then # then
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let "value = 0 - $1" # change sign,
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else # else
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let "value = $1" # leave it alone.
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fi
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}
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if [ $# -ne "$ARGS" ] # Require two command line params.
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then
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Param_Error
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fi
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Parse_Date $1
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check_date $day $month $year # See if valid date.
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strip_leading_zero $day # Remove any leading zeroes
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day=$? # on day and/or month.
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strip_leading_zero $month
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month=$?
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day_index $day $month $year
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date1=$?
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abs $date1 # Make sure it's positive
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date1=$value # by getting absolute value.
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Parse_Date $2
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check_date $day $month $year
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strip_leading_zero $day
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day=$?
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strip_leading_zero $month
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month=$?
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day_index $day $month $year
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date2=$?
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abs $date2 # Make sure it's positive.
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date2=$value
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calculate_difference $date1 $date2
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abs $diff # Make sure it's positive.
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diff=$value
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echo $diff
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exit 0
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# Compare this script with the implementation of Gauss' Formula in C at
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# http://buschencrew.hypermart.net/software/datedif
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#!/bin/bash
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# de-rpm.sh: Unpack an 'rpm' archive
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E_NO_ARGS=65
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TEMPFILE=$$.cpio # Tempfile with "unique" name.
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# $$ is process ID of script.
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if [ -z "$1" ]
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then
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echo "Usage: `basename $0` filename"
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exit $E_NO_ARGS
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fi
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rpm2cpio < $1 > $TEMPFILE # Converts rpm archive into cpio archive.
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cpio --make-directories -F $TEMPFILE -i # Unpacks cpio archive.
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rm -f $TEMPFILE # Deletes cpio archive.
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exit 0
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#!/bin/bash
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# erase.sh: Using "stty" to set an erase character when reading input.
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echo -n "What is your name? "
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read name # Try to erase characters of input.
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# Won't work.
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echo "Your name is $name."
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stty erase '#' # Set "hashmark" (#) as erase character.
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echo -n "What is your name? "
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read name # Use # to erase last character typed.
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echo "Your name is $name."
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exit 0
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#!/bin/bash
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echo
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echo "String operations using \"expr $string :\" construct"
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echo "-------------------------------------------"
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echo
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a=1234zipper43231
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echo "The string being operated upon is \"`expr "$a" : '\(.*\)'`\"."
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# Escaped parentheses.
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# Regular expression parsing.
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echo "Length of \"$a\" is `expr "$a" : '.*'`." # Length of string
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echo "Number of digits at the beginning of \"$a\" is `expr "$a" : '[0-9]*'`."
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echo "The digits at the beginning of \"$a\" are `expr "$a" : '\([0-9]*\)'`."
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echo
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exit 0
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#!/bin/bash
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# max2.sh: Maximum of two LARGE integers.
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# This is the previous "max.sh" example,
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# modified to permit comparing large integers.
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EQUAL=0 # Return value if both params equal.
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MAXRETVAL=256 # Maximum positive return value from a function.
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E_PARAM_ERR=-99999 # Parameter error.
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E_NPARAM_ERR=99999 # "Normalized" parameter error.
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max2 () # Returns larger of two numbers.
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{
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if [ -z "$2" ]
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then
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return $E_PARAM_ERR
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fi
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if [ "$1" -eq "$2" ]
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then
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return $EQUAL
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else
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if [ "$1" -gt "$2" ]
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then
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retval=$1
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else
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retval=$2
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fi
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fi
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# -------------------------------------------------------------- #
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# This is a workaround to enable returning a large integer
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# from this function.
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if [ "$retval" -gt "$MAXRETVAL" ] # If out of range,
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then # then
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let "retval = (( 0 - $retval ))" # adjust to a negative value.
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# (( 0 - $VALUE )) changes the sign of VALUE.
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fi
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# Large *negative* return values permitted, fortunately.
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# -------------------------------------------------------------- #
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return $retval
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}
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max2 33001 33997
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return_val=$?
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# -------------------------------------------------------------------------- #
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if [ "$return_val" -lt 0 ] # If "adjusted" negative number,
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then # then
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let "return_val = (( 0 - $return_val ))" # renormalize to positive.
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fi # "Absolute value" of $return_val.
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# -------------------------------------------------------------------------- #
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if [ "$return_val" -eq "$E_NPARAM_ERR" ]
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then # Parameter error "flag" gets sign changed, too.
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echo "Error: Too few parameters."
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elif [ "$return_val" -eq "$EQUAL" ]
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then
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echo "The two numbers are equal."
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else
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echo "The larger of the two numbers is $return_val."
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fi
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exit 0
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@ -0,0 +1,30 @@
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#!/bin/bash
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echo
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echo "Enter a string terminated by a \\, then press <ENTER>."
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echo "Then, enter a second string, and again press <ENTER>."
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read var1 # The "\" suppresses the newline, when reading "var1".
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# first line \
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# second line
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echo "var1 = $var1"
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# var1 = first line second line
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# For each line terminated by a "\",
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# you get a prompt on the next line to continue feeding characters into var1.
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echo; echo
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echo "Enter another string terminated by a \\ , then press <ENTER>."
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read -r var2 # The -r option causes the "\" to be read literally.
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# first line \
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echo "var2 = $var2"
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# var2 = first line \
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# Data entry terminates with the first <ENTER>.
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echo
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exit 0
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@ -0,0 +1,23 @@
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#!/bin/bash
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# return-test.sh
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# The largest positive value a function can return is 256.
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return_test () # Returns whatever passed to it.
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{
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return $1
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}
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return_test 27 # o.k.
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echo $? # Returns 27.
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return_test 256 # Still o.k.
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echo $? # Returns 256.
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return_test 257 # Error!
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echo $? # Returns 1 (return code for miscellaneous error).
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return_test -151896 # However, large negative numbers work.
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echo $? # Returns -151896.
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exit 0
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@ -0,0 +1,33 @@
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#!/bin/bash
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# Pattern replacement at prefix / suffix of string.
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v0=abc1234zip1234abc # Original variable.
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echo "v0 = $v0" # abc1234zip1234abc
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echo
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# Match at prefix (beginning) of string.
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v1=${v0/#abc/ABCDEF} # abc1234zip1234abc
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# |-|
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echo "v1 = $v1" # ABCDE1234zip1234abc
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# |---|
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# Match at suffix (end) of string.
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v2=${v0/%abc/ABCDEF} # abc1234zip123abc
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# |-|
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echo "v2 = $v2" # abc1234zip1234ABCDEF
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# |----|
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echo
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# ----------------------------------------------------
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# Must match at beginning / end of string,
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#+ otherwise no replacement results.
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# ----------------------------------------------------
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v3=${v0/#123/000} # Matches, but not at beginning.
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echo "v3 = $v3" # abc1234zip1234abc
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# NO REPLACEMENT.
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v4=${v0/%123/000} # Matches, but not at end.
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echo "v4 = $v4" # abc1234zip1234abc
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# NO REPLACEMENT.
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exit 0
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