linux shell bash 精彩脚本示例,Linux Shell Bash 精彩脚本示例(2)

蔚落 2023-01-20 14:53 19阅读 0赞

34 echo; echo "Done copying $OF to CDR on device $CDROM."

36 echo "Do you want to erase the image file (y/n)? " \# Probably a huge file.

37 read answer

39 case "$answer" in

40 \[yY\]) rm -f $OF

41 echo "$OF erased."

42 ;;

43 \*) echo "$OF not erased.";;

44 esac

46 echo

48 \# Exercise:

49 \# Change the above "case" statement to also accept "yes" and "Yes" as input.

51 exit 0

例子 A-6. Collatz序列

1 \#!/bin/bash

2 \# collatz.sh

4 \# The notorious "hailstone" or Collatz series.

5 \# -------------------------------------------

6 \# 1) Get the integer "seed" from the command line.

7 \# 2) NUMBER

8 \# 3) Print NUMBER.

9 \# 4) If NUMBER is even, divide by 2, or

10 \# 5)+ if odd, multiply by 3 and add 1.

11 \# 6) NUMBER

12 \# 7) Loop back to step 3 (for specified number of iterations).

13 \#

14 \# The theory is that every sequence,

15 \#+ no matter how large the initial value,

16 \#+ eventually settles down to repeating "4,2,1..." cycles,

17 \#+ even after fluctuating through a wide range of values.

18 \#

19 \# This is an instance of an "iterate",

20 \#+ an operation that feeds its output back into the input.

21 \# Sometimes the result is a "chaotic" series.

24 MAX\_ITERATIONS=200

25 \# For large seed numbers (>32000), increase MAX\_ITERATIONS.

27 h=$\{1:-$$\} \# Seed

28 \# Use $PID as seed,

29 \#+ if not specified as command-line arg.

31 echo

32 echo "C($h) --- $MAX\_ITERATIONS Iterations"

33 echo

35 for ((i=1; i<=MAX\_ITERATIONS; i++))

36 do

38 echo -n "$h "

39 \# ^^^^^

40 \# tab

42 let "remainder = h % 2"

43 if \[ "$remainder" -eq 0 \] \# Even?

44 then

45 let "h /= 2" \# Divide by 2.

46 else

47 let "h = h\*3 + 1" \# Multiply by 3 and add 1.

48 fi

51 COLUMNS=10 \# Output 10 values per line.

52 let "line\_break = i % $COLUMNS"

53 if \[ "$line\_break" -eq 0 \]

54 then

55 echo

56 fi

58 done

60 echo

62 \# For more information on this mathematical function,

63 \#+ see "Computers, Pattern, Chaos, and Beauty", by Pickover, p. 185 ff.,

64 \#+ as listed in the bibliography.

66 exit 0

例子 A-7. days-between: 计算两个日期之间天数差

1 \#!/bin/bash

2 \# days-between.sh: Number of days between two dates.

3 \# Usage: ./days-between.sh \[M\]M/\[D\]D/YYYY \[M\]M/\[D\]D/YYYY

4 \#

5 \# Note: Script modified to account for changes in Bash 2.05b

6 \#+ that closed the loophole permitting large negative

7 \#+ integer return values.

9 ARGS=2 \# Two command line parameters expected.

10 E\_PARAM\_ERR=65 \# Param error.

12 REFYR=1600 \# Reference year.

13 CENTURY=100

14 DIY=365

15 ADJ\_DIY=367 \# Adjusted for leap year + fraction.

16 MIY=12

17 DIM=31

18 LEAPCYCLE=4

20 MAXRETVAL=255 \# Largest permissable

21 \#+ positive return value from a function.

23 diff= \# Declare global variable for date difference.

24 value= \# Declare global variable for absolute value.

25 day= \# Declare globals for day, month, year.

26 month=

27 year=

30 Param\_Error () \# Command line parameters wrong.

31 \{

32 echo "Usage: \`basename $0\` \[M\]M/\[D\]D/YYYY \[M\]M/\[D\]D/YYYY"

33 echo " (date must be after 1/3/1600)"

34 exit $E\_PARAM\_ERR

35 \}

38 Parse\_Date () \# Parse date from command line params.

39 \{

40 month=$\{1%%\}

43 let "year = \`basename $1\`" \# Not a filename, but works just the same.

44 \}

47 check\_date () \# Checks for invalid date(s) passed.

48 \{

49 \[ "$day" -gt "$DIM" \] || \[ "$month" -gt "$MIY" \] || \[ "$year" -lt "$REFYR" \] && Param\_Error

50 \# Exit script on bad value(s).

51 \# Uses "or-list / and-list".

52 \#

53 \# Exercise: Implement more rigorous date checking.

54 \}

57 strip\_leading\_zero () \# Better to strip possible leading zero(s)

58 \{ \#+ from day and/or month

59 return $\{1\#0\} \#+ since otherwise Bash will interpret them

60 \} \#+ as octal values (POSIX.2, sect 2.9.2.1).

63 day\_index () \# Gauss' Formula:

64 \{ \# Days from Jan. 3, 1600 to date passed as param.

66 day=$1

67 month=$2

68 year=$3

70 let "month = $month - 2"

71 if \[ "$month" -le 0 \]

72 then

73 let "month += 12"

74 let "year -= 1"

75 fi

77 let "year -= $REFYR"

78 let "indexyr = $year / $CENTURY"

81 let "Days = $DIY\*$year + $year/$LEAPCYCLE - $indexyr + $indexyr/$LEAPCYCLE + $ADJ\_DIY\*$month/$MIY + $day - $DIM"

82 \# For an in-depth explanation of this algorithm, see

83 \#+ http://home.t-online.de/home/berndt.schwerdtfeger/cal.htm

86 echo $Days

88 \}

91 calculate\_difference () \# Difference between to day indices.

92 \{

93 let "diff = $1 - $2" \# Global variable.

94 \}

97 abs () \# Absolute value

98 \{ \# Uses global "value" variable.

99 if \[ "$1" -lt 0 \] \# If negative

100 then \#+ then

101 let "value = 0 - $1" \#+ change sign,

102 else \#+ else

103 let "value = $1" \#+ leave it alone.

104 fi

105 \}

106

107

108

109 if \[ $\# -ne "$ARGS" \] \# Require two command line params.

110 then

111 Param\_Error

112 fi

113

114 Parse\_Date $1

115 check\_date $day $month $year \# See if valid date.

116

117 strip\_leading\_zero $day \# Remove any leading zeroes

118 day=$? \#+ on day and/or month.

119 strip\_leading\_zero $month

120 month=$?

121

122 let "date1 = \`day\_index $day $month $year\`"

123

124

125 Parse\_Date $2

126 check\_date $day $month $year

127

128 strip\_leading\_zero $day

129 day=$?

130 strip\_leading\_zero $month

131 month=$?

132

133 date2=$(day\_index $day $month $year) \# Command substitution.

134

135

136 calculate\_difference $date1 $date2

137

138 abs $diff \# Make sure it's positive.

139 diff=$value

140

141 echo $diff

142

143 exit 0

144 \# Compare this script with

145 \#+ the implementation of Gauss' Formula in a C program at:

146 \#+ http://buschencrew.hypermart.net/software/datedif

例子 A-8. 构造一个"字典"

1 \#!/bin/bash

2 \# makedict.sh \[make dictionary\]

4 \# Modification of /usr/sbin/mkdict script.

6 \#

7 \# This modified script included in this document in a manner

8 \#+ consistent with the "LICENSE" document of the "Crack" package

9 \#+ that the original script is a part of.

linux shell bash 精彩脚本示例,Linux Shell Bash 精彩脚本示例(2)

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