contributed-scripts.html

Shall高级编程

  15 
  16 echo; echo "Copying the source CD to $OF."
  17 echo "This may take a while. Please be patient."
  18 
  19 dd if=$CDROM of=$OF bs=$BLOCKSIZE          # Raw device copy.
  20 
  21 
  22 echo; echo "Remove data CD."
  23 echo "Insert blank CDR."
  24 echo "Press ENTER when ready. "
  25 read ready                                 # Wait for input, $ready not used.
  26 
  27 echo "Copying $OF to CDR."
  28 
  29 cdrecord -v -isosize speed=$SPEED dev=$DEVICE $OF
  30 # Uses Joerg Schilling's "cdrecord" package (see its docs).
  31 # http://www.fokus.gmd.de/nthp/employees/schilling/cdrecord.html
  32 
  33 
  34 echo; echo "Done copying $OF to CDR on device $CDROM."
  35 
  36 echo "Do you want to erase the image file (y/n)? "  # Probably a huge file.
  37 read answer
  38 
  39 case "$answer" in
  40 [yY]) rm -f $OF
  41       echo "$OF erased."
  42       ;;
  43 *)    echo "$OF not erased.";;
  44 esac
  45 
  46 echo
  47 
  48 # Exercise:
  49 # Change the above "case" statement to also accept "yes" and "Yes" as input.
  50 
  51&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="COLLATZ"
></A
><P
><B
>Example A-6. Collatz series</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# collatz.sh
   3&nbsp;
   4&nbsp;#  The notorious "hailstone" or Collatz series.
   5&nbsp;#  -------------------------------------------
   6&nbsp;#  1) Get the integer "seed" from the command line.
   7&nbsp;#  2) NUMBER &#60;--- seed
   8&nbsp;#  3) Print NUMBER.
   9&nbsp;#  4)  If NUMBER is even, divide by 2, or
  10&nbsp;#  5)+ if odd, multiply by 3 and add 1.
  11&nbsp;#  6) NUMBER &#60;--- result 
  12&nbsp;#  7) Loop back to step 3 (for specified number of iterations).
  13&nbsp;#
  14&nbsp;#  The theory is that every sequence,
  15&nbsp;#+ no matter how large the initial value,
  16&nbsp;#+ eventually settles down to repeating "4,2,1..." cycles,
  17&nbsp;#+ even after fluctuating through a wide range of values.
  18&nbsp;#
  19&nbsp;#  This is an instance of an "iterate,"
  20&nbsp;#+ an operation that feeds its output back into the input.
  21&nbsp;#  Sometimes the result is a "chaotic" series.
  22&nbsp;
  23&nbsp;
  24&nbsp;MAX_ITERATIONS=200
  25&nbsp;# For large seed numbers (&#62;32000), increase MAX_ITERATIONS.
  26&nbsp;
  27&nbsp;h=${1:-$$}                      #  Seed
  28&nbsp;                                #  Use $PID as seed,
  29&nbsp;                                #+ if not specified as command-line arg.
  30&nbsp;
  31&nbsp;echo
  32&nbsp;echo "C($h) --- $MAX_ITERATIONS Iterations"
  33&nbsp;echo
  34&nbsp;
  35&nbsp;for ((i=1; i&#60;=MAX_ITERATIONS; i++))
  36&nbsp;do
  37&nbsp;
  38&nbsp;echo -n "$h	"
  39&nbsp;#          ^^^^^
  40&nbsp;#           tab
  41&nbsp;
  42&nbsp;  let "remainder = h % 2"
  43&nbsp;  if [ "$remainder" -eq 0 ]   # Even?
  44&nbsp;  then
  45&nbsp;    let "h /= 2"              # Divide by 2.
  46&nbsp;  else
  47&nbsp;    let "h = h*3 + 1"         # Multiply by 3 and add 1.
  48&nbsp;  fi
  49&nbsp;
  50&nbsp;
  51&nbsp;COLUMNS=10                    # Output 10 values per line.
  52&nbsp;let "line_break = i % $COLUMNS"
  53&nbsp;if [ "$line_break" -eq 0 ]
  54&nbsp;then
  55&nbsp;  echo
  56&nbsp;fi  
  57&nbsp;
  58&nbsp;done
  59&nbsp;
  60&nbsp;echo
  61&nbsp;
  62&nbsp;#  For more information on this mathematical function,
  63&nbsp;#+ see _Computers, Pattern, Chaos, and Beauty_, by Pickover, p. 185 ff.,
  64&nbsp;#+ as listed in the bibliography.
  65&nbsp;
  66&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
><A
NAME="DAYSBETWEEN0"
></A
></P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="DAYSBETWEEN"
></A
><P
><B
>Example A-7. <I
CLASS="FIRSTTERM"
>days-between</I
>: Days between two
        dates</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# days-between.sh:    Number of days between two dates.
   3&nbsp;# Usage: ./days-between.sh [M]M/[D]D/YYYY [M]M/[D]D/YYYY
   4&nbsp;#
   5&nbsp;# Note: Script modified to account for changes in Bash, v. 2.05b +,
   6&nbsp;#+      that closed the loophole permitting large negative
   7&nbsp;#+      integer return values.
   8&nbsp;
   9&nbsp;ARGS=2                # Two command line parameters expected.
  10&nbsp;E_PARAM_ERR=65        # Param error.
  11&nbsp;
  12&nbsp;REFYR=1600            # Reference year.
  13&nbsp;CENTURY=100
  14&nbsp;DIY=365
  15&nbsp;ADJ_DIY=367           # Adjusted for leap year + fraction.
  16&nbsp;MIY=12
  17&nbsp;DIM=31
  18&nbsp;LEAPCYCLE=4
  19&nbsp;
  20&nbsp;MAXRETVAL=255         #  Largest permissible
  21&nbsp;                      #+ positive return value from a function.
  22&nbsp;
  23&nbsp;diff=                 # Declare global variable for date difference.
  24&nbsp;value=                # Declare global variable for absolute value.
  25&nbsp;day=                  # Declare globals for day, month, year.
  26&nbsp;month=
  27&nbsp;year=
  28&nbsp;
  29&nbsp;
  30&nbsp;Param_Error ()        # Command line parameters wrong.
  31&nbsp;{
  32&nbsp;  echo "Usage: `basename $0` [M]M/[D]D/YYYY [M]M/[D]D/YYYY"
  33&nbsp;  echo "       (date must be after 1/3/1600)"
  34&nbsp;  exit $E_PARAM_ERR
  35&nbsp;}  
  36&nbsp;
  37&nbsp;
  38&nbsp;Parse_Date ()                 # Parse date from command line params.
  39&nbsp;{
  40&nbsp;  month=${1%%/**}
  41&nbsp;  dm=${1%/**}                 # Day and month.
  42&nbsp;  day=${dm#*/}
  43&nbsp;  let "year = `basename $1`"  # Not a filename, but works just the same.
  44&nbsp;}  
  45&nbsp;
  46&nbsp;
  47&nbsp;check_date ()                 # Checks for invalid date(s) passed.
  48&nbsp;{
  49&nbsp;  [ "$day" -gt "$DIM" ] || [ "$month" -gt "$MIY" ] ||
  50&nbsp;  [ "$year" -lt "$REFYR" ] &#38;&#38; Param_Error
  51&nbsp;  # Exit script on bad value(s).
  52&nbsp;  # Uses or-list / and-list.
  53&nbsp;  #
  54&nbsp;  # Exercise: Implement more rigorous date checking.
  55&nbsp;}
  56&nbsp;
  57&nbsp;
  58&nbsp;strip_leading_zero () #  Better to strip possible leading zero(s)
  59&nbsp;{                     #+ from day and/or month
  60&nbsp;  return ${1#0}       #+ since otherwise Bash will interpret them
  61&nbsp;}                     #+ as octal values (POSIX.2, sect 2.9.2.1).
  62&nbsp;
  63&nbsp;
  64&nbsp;day_index ()          # Gauss' Formula:
  65&nbsp;{                     # Days from March 1, 1600 to date passed as param.
  66&nbsp;                      #           ^^^^^^^^^^^^^
  67&nbsp;  day=$1
  68&nbsp;  month=$2
  69&nbsp;  year=$3
  70&nbsp;
  71&nbsp;  let "month = $month - 2"
  72&nbsp;  if [ "$month" -le 0 ]
  73&nbsp;  then
  74&nbsp;    let "month += 12"
  75&nbsp;    let "year -= 1"
  76&nbsp;  fi  
  77&nbsp;
  78&nbsp;  let "year -= $REFYR"
  79&nbsp;  let "indexyr = $year / $CENTURY"
  80&nbsp;
  81&nbsp;
  82&nbsp;  let "Days = $DIY*$year + $year/$LEAPCYCLE - $indexyr \
  83&nbsp;              + $indexyr/$LEAPCYCLE + $ADJ_DIY*$month/$MIY + $day - $DIM"
  84&nbsp;  #  For an in-depth explanation of this algorithm, see
  85&nbsp;  #+   http://weblogs.asp.net/pgreborio/archive/2005/01/06/347968.aspx
  86&nbsp;
  87&nbsp;
  88&nbsp;  echo $Days
  89&nbsp;
  90&nbsp;}  
  91&nbsp;
  92&nbsp;
  93&nbsp;calculate_difference ()            # Difference between two day indices.
  94&nbsp;{
  95&nbsp;  let "diff = $1 - $2"             # Global variable.
  96&nbsp;}  
  97&nbsp;
  98&nbsp;
  99&nbsp;abs ()                             #  Absolute value
 100&nbsp;{                                  #  Uses global "value" variable.
 101&nbsp;  if [ "$1" -lt 0 ]                #  If negative
 102&nbsp;  then                             #+ then
 103&nbsp;    let "value = 0 - $1"           #+ change sign,
 104&nbsp;  else                             #+ else
 105&nbsp;    let "value = $1"               #+ leave it alone.
 106&nbsp;  fi
 107&nbsp;}
 108&nbsp;
 109&nbsp;
 110&nbsp;
 111&nbsp;if [ $# -ne "$ARGS" ]              # Require two command line params.
 112&nbsp;then
 113&nbsp;  Param_Error
 114&nbsp;fi  
 115&nbsp;
 116&nbsp;Parse_Date $1
 117&nbsp;check_date $day $month $year       #  See if valid date.
 118&nbsp;
 119&nbsp;strip_leading_zero $day            #  Remove any leading zeroes
 120&nbsp;day=$?                             #+ on day and/or month.
 121&nbsp;strip_leading_zero $month
 122&nbsp;month=$?
 123&nbsp;
 124&nbsp;let "date1 = `day_index $day $month $year`"
 125&nbsp;
 126&nbsp;
 127&nbsp;Parse_Date $2
 128&nbsp;check_date $day $month $year
 129&nbsp;
 130&nbsp;strip_leading_zero $day
 131&nbsp;day=$?
 132&nbsp;strip_leading_zero $month
 133&nbsp;month=$?
 134&nbsp;
 135&nbsp;date2=$(day_index $day $month $year) # Command substitution.
 136&nbsp;
 137&nbsp;
 138&nbsp;calculate_difference $date1 $date2
 139&nbsp;
 140&nbsp;abs $diff                            # Make sure it's positive.
 141&nbsp;diff=$value
 142&nbsp;
 143&nbsp;echo $diff
 144&nbsp;
 145&nbsp;exit 0
 146&nbsp;
 147&nbsp;#  Compare this script with
 148&nbsp;#+ the implementation of Gauss' Formula in a C program at:
 149&nbsp;#+    http://buschencrew.hypermart.net/software/datedif</PRE
></TD
></TR
></TABLE
><HR></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="MAKEDICT"
></A
><P
><B
>Example A-8. Making a <I
CLASS="FIRSTTERM"
>dictionary</I
></B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# makedict.sh  [make dictionary]
   3&nbsp;
   4&nbsp;# Modification of /usr/sbin/mkdict (/usr/sbin/cracklib-forman) script.
   5&nbsp;# Original script copyright 1993, by Alec Muffett.
   6&nbsp;#
   7&nbsp;#  This modified script included in this document in a manner
   8&nbsp;#+ consistent with the "LICENSE" document of the "Crack" package
   9&nbsp;#+ that the original script is a part of.
  10&nbsp;
  11&nbsp;#  This script processes text files to produce a sorted list
  12&nbsp;#+ of words found in the files.
  13&nbsp;#  This may be useful for compiling dictionaries
  14&nbsp;#+ and for other lexicographic purposes.
  15&nbsp;
  16&nbsp;
  17&nbsp;E_BADARGS=65
  18&nbsp;
  19&nbsp;if [ ! -r "$1" ]                    #  Need at least one
  20&nbsp;then                                #+ valid file argument.
  21&nbsp;  echo "Usage: $0 files-to-process"
  22&nbsp;  exit $E_BADARGS
  23&nbsp;fi  
  24&nbsp;
  25&nbsp;
  26&nbsp;# SORT="sort"                       #  No longer necessary to define options
  27&nbsp;                                    #+ to sort. Changed from original script.
  28&nbsp;
  29&nbsp;cat $* |                            # Contents of specified files to stdout.
  30&nbsp;        tr A-Z a-z |                # Convert to lowercase.
  31&nbsp;        tr ' ' '\012' |             # New: change spaces to newlines.
  32&nbsp;#       tr -cd '\012[a-z][0-9]' |   #  Get rid of everything non-alphanumeric
  33&nbsp;                                    #+ (in original script).
  34&nbsp;        tr -c '\012a-z'  '\012' |   #  Rather than deleting non-alpha chars,
  35&nbsp;                                    #+ change them to newlines.
  36&nbsp;        sort |                      # $SORT options unnecessary now.
  37&nbsp;        uniq |                      # Remove duplicates.
  38&nbsp;        grep -v '^#' |              # Delete lines beginning with a hashmark.
  39&nbsp;        grep -v '^$'                # Delete blank lines.
  40&nbsp;
  41&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
><A
NAME="SOUNDEX0"
></A
></P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="SOUNDEX"
></A
><P
><B
>Example A-9. Soundex conversion</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# soundex.sh: Calculate "soundex" code for names
   3&nbsp;
   4&nbsp;# =======================================================
   5&nbsp;#        Soundex script
   6&nbsp;#              by
   7&nbsp;#         Mendel Cooper
   8&nbsp;#     [e-mail]
   9&nbsp;#       23 January, 2002
  10&nbsp;#
  11&nbsp;#   Placed in the Public Domain.
  12&nbsp;#
  13&nbsp;# A slightly different version of this script appeared in
  14&nbsp;#+ Ed Schaefer's July, 2002 "Shell Corner" column
  15&nbsp;#+ in "Unix Review" on-line,
  16&nbsp;#+ http://www.unixreview.com/documents/uni1026336632258/
  17&nbsp;# =======================================================
  18&nbsp;
  19&nbsp;
  20&nbsp;ARGCOUNT=1                     # Need name as argument.