bash学习备忘录

教材: LINUX SHELL编程从学习到精通

1.shell怎样输出换行

在做例:8-24例子时候有需要加入回车

教材中使用是

echo "" #换行

作者使用的是fedora,我使用的是ubuntu 14.04,这个不起作用

使用

echo -e ""可以,

如果使用

echo -e "\n"

就会回车两次了.

2. 在13.6.2 不使用局部变量的递归中代码好像有问题,参考新代码:

#!/bin/bash

move=0

dohanoi()

{

   if [ $1 -eq 0 ]

   then

      echo -n ""

   elif [ $1 -eq 1 ]

   then

      echo "move $2 ----> $4"

      let "move=move+1"

      echo "move=$move"

   elif [ $1 -eq 2 ]

   then

      echo "move $2 ----> $3"

      let "move=move+1"

      echo "move=$move"

      echo "move $2 ----> $4"

      let "move=move+1"

      echo "move=$move"

      echo "move $3 ----> $4"

      let "move=move+1"

      echo "move=$move"

   else

      dohanoi "$(($1-1))" $2 $4 $3

      echo "move $2 ----> $4"

      let "move=move+1"

      echo "move=$move"

      dohanoi "$(($1-1))" $3 $2 $4

   fi

  }

echo "Please input the num of disk:"

  read num

  dohanoi $num 'A' 'B' 'C'

  echo "move=$move"

3.特别需要注意if语句中的空格

 if ["$num" -eq 0 ]

由于缺少相应的空格会提示:

./function13.sh: 行 5: [-1579: 未找到命令

4.在例子15-12中:

#!/bin/bash

echo "number of arguments is $#"

echo "What you input is: "

while [[ "$*" != "" ]]

do

    echo "$1"

    shift

done

如果把""改成" ",那会导致无限循环输出空.

5.在例子16-11中:

#!/bin/bash

trap 'echo "before execute line:$LINENO,a=$a,b=$b,c=$c"' DEBUG

a=0

b=2

c=100

while :

do

        if (( a >= 10 ))

         then

           break

        fi

        let "a=a+2"

        let "b=b*2"

        let "c=C-10"

done

sh -x trapdebug.sh

输出结果:

+ trap echo "before execute line:$LINENO,a=$a,b=$b,c=$c" DEBUG

trap: DEBUG: bad trap

+ a=0

+ b=2

+ c=100

+ :

+ a 10

trapdebug.sh: 10: trapdebug.sh: a: not found

+ let a=a+2

trapdebug.sh: 14: trapdebug.sh: let: not found

+ let b=b*2

trapdebug.sh: 15: trapdebug.sh: let: not found

+ let c=C-10

trapdebug.sh: 16: trapdebug.sh: let: not found

+ :

+ a 10

trapdebug.sh: 10: trapdebug.sh: a: not found

+ let a=a+2

trapdebug.sh: 14: trapdebug.sh: let: not found

+ let b=b*2

trapdebug.sh: 15: trapdebug.sh: let: not found

+ let c=C-10

trapdebug.sh: 16: trapdebug.sh: let: not found

+ :

+ a 10

trapdebug.sh: 10: trapdebug.sh: a: not found

+ let a=a+2

trapdebug.sh: 14: trapdebug.sh: let: not found

+ let b=b*2

trapdebug.sh: 15: trapdebug.sh: let: not found

+ let c=C-10

trapdebug.sh: 16: trapdebug.sh: let: not found

+ :

+ a 10

trapdebug.sh: 10: trapdebug.sh: a: not found

+ let a=a+2

trapdebug.sh: 14: trapdebug.sh: let: not found

修改文件:

#!/bin/bash

trap 'echo "before execute line:$LINENO,a=$a,b=$b,c=$c"' DEBUG

a=0

b=2

c=100

while :

do

        if (( a >= 10 ))

         then

           break

        fi

        let "a=a+2"

        let "b=b*2"

        let "c=C-10"

done

运行./trapdebug.sh

+ trap 'echo "before execute line:$LINENO,a=$a,b=$b,c=$c"' DEBUG

++ echo 'before execute line:5,a=,b=,c='

before execute line:5,a=,b=,c=

+ a=0

++ echo 'before execute line:6,a=0,b=,c='

before execute line:6,a=0,b=,c=

+ b=2

++ echo 'before execute line:7,a=0,b=2,c='

before execute line:7,a=0,b=2,c=

+ c=100

++ echo 'before execute line:8,a=0,b=2,c=100'

before execute line:8,a=0,b=2,c=100

+ :

++ echo 'before execute line:10,a=0,b=2,c=100'

before execute line:10,a=0,b=2,c=100

+ ((  a >= 10  ))

++ echo 'before execute line:14,a=0,b=2,c=100'

before execute line:14,a=0,b=2,c=100

+ let a=a+2

++ echo 'before execute line:15,a=2,b=2,c=100'

before execute line:15,a=2,b=2,c=100

+ let 'b=b*2'

++ echo 'before execute line:16,a=2,b=4,c=100'

before execute line:16,a=2,b=4,c=100

+ let c=C-10

++ echo 'before execute line:8,a=2,b=4,c=-10'

before execute line:8,a=2,b=4,c=-10

+ :

++ echo 'before execute line:10,a=2,b=4,c=-10'

before execute line:10,a=2,b=4,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:14,a=2,b=4,c=-10'

before execute line:14,a=2,b=4,c=-10

+ let a=a+2

++ echo 'before execute line:15,a=4,b=4,c=-10'

before execute line:15,a=4,b=4,c=-10

+ let 'b=b*2'

++ echo 'before execute line:16,a=4,b=8,c=-10'

before execute line:16,a=4,b=8,c=-10

+ let c=C-10

++ echo 'before execute line:8,a=4,b=8,c=-10'

before execute line:8,a=4,b=8,c=-10

+ :

++ echo 'before execute line:10,a=4,b=8,c=-10'

before execute line:10,a=4,b=8,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:14,a=4,b=8,c=-10'

before execute line:14,a=4,b=8,c=-10

+ let a=a+2

++ echo 'before execute line:15,a=6,b=8,c=-10'

before execute line:15,a=6,b=8,c=-10

+ let 'b=b*2'

++ echo 'before execute line:16,a=6,b=16,c=-10'

before execute line:16,a=6,b=16,c=-10

+ let c=C-10

++ echo 'before execute line:8,a=6,b=16,c=-10'

before execute line:8,a=6,b=16,c=-10

+ :

++ echo 'before execute line:10,a=6,b=16,c=-10'

before execute line:10,a=6,b=16,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:14,a=6,b=16,c=-10'

before execute line:14,a=6,b=16,c=-10

+ let a=a+2

++ echo 'before execute line:15,a=8,b=16,c=-10'

before execute line:15,a=8,b=16,c=-10

+ let 'b=b*2'

++ echo 'before execute line:16,a=8,b=32,c=-10'

before execute line:16,a=8,b=32,c=-10

+ let c=C-10

++ echo 'before execute line:8,a=8,b=32,c=-10'

before execute line:8,a=8,b=32,c=-10

+ :

++ echo 'before execute line:10,a=8,b=32,c=-10'

before execute line:10,a=8,b=32,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:14,a=8,b=32,c=-10'

before execute line:14,a=8,b=32,c=-10

+ let a=a+2

++ echo 'before execute line:15,a=10,b=32,c=-10'

before execute line:15,a=10,b=32,c=-10

+ let 'b=b*2'

++ echo 'before execute line:16,a=10,b=64,c=-10'

before execute line:16,a=10,b=64,c=-10

+ let c=C-10

++ echo 'before execute line:8,a=10,b=64,c=-10'

before execute line:8,a=10,b=64,c=-10

+ :

++ echo 'before execute line:10,a=10,b=64,c=-10'

before execute line:10,a=10,b=64,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:12,a=10,b=64,c=-10'

before execute line:12,a=10,b=64,c=-10

+ break

如果修改成:

#!/bin/bash

trap 'echo "before execute line:$LINENO,a=$a,b=$b,c=$c"' DEBUG

set -x

a=0

b=2

c=100

while :

do

        if (( a >= 10 ))

         then

           break

        fi

        let "a=a+2"

        let "b=b*2"

        let "c=C-10"

done

运行结果:

before execute line:3,a=,b=,c=

++ echo 'before execute line:4,a=,b=,c='

before execute line:4,a=,b=,c=

+ a=0

++ echo 'before execute line:5,a=0,b=,c='

before execute line:5,a=0,b=,c=

+ b=2

++ echo 'before execute line:6,a=0,b=2,c='

before execute line:6,a=0,b=2,c=

+ c=100

++ echo 'before execute line:7,a=0,b=2,c=100'

before execute line:7,a=0,b=2,c=100

+ :

++ echo 'before execute line:9,a=0,b=2,c=100'

before execute line:9,a=0,b=2,c=100

+ ((  a >= 10  ))

++ echo 'before execute line:13,a=0,b=2,c=100'

before execute line:13,a=0,b=2,c=100

+ let a=a+2

++ echo 'before execute line:14,a=2,b=2,c=100'

before execute line:14,a=2,b=2,c=100

+ let 'b=b*2'

++ echo 'before execute line:15,a=2,b=4,c=100'

before execute line:15,a=2,b=4,c=100

+ let c=C-10

++ echo 'before execute line:7,a=2,b=4,c=-10'

before execute line:7,a=2,b=4,c=-10

+ :

++ echo 'before execute line:9,a=2,b=4,c=-10'

before execute line:9,a=2,b=4,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:13,a=2,b=4,c=-10'

before execute line:13,a=2,b=4,c=-10

+ let a=a+2

++ echo 'before execute line:14,a=4,b=4,c=-10'

before execute line:14,a=4,b=4,c=-10

+ let 'b=b*2'

++ echo 'before execute line:15,a=4,b=8,c=-10'

before execute line:15,a=4,b=8,c=-10

+ let c=C-10

++ echo 'before execute line:7,a=4,b=8,c=-10'

before execute line:7,a=4,b=8,c=-10

+ :

++ echo 'before execute line:9,a=4,b=8,c=-10'

before execute line:9,a=4,b=8,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:13,a=4,b=8,c=-10'

before execute line:13,a=4,b=8,c=-10

+ let a=a+2

++ echo 'before execute line:14,a=6,b=8,c=-10'

before execute line:14,a=6,b=8,c=-10

+ let 'b=b*2'

++ echo 'before execute line:15,a=6,b=16,c=-10'

before execute line:15,a=6,b=16,c=-10

+ let c=C-10

++ echo 'before execute line:7,a=6,b=16,c=-10'

before execute line:7,a=6,b=16,c=-10

+ :

++ echo 'before execute line:9,a=6,b=16,c=-10'

before execute line:9,a=6,b=16,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:13,a=6,b=16,c=-10'

before execute line:13,a=6,b=16,c=-10

+ let a=a+2

++ echo 'before execute line:14,a=8,b=16,c=-10'

before execute line:14,a=8,b=16,c=-10

+ let 'b=b*2'

++ echo 'before execute line:15,a=8,b=32,c=-10'

before execute line:15,a=8,b=32,c=-10

+ let c=C-10

++ echo 'before execute line:7,a=8,b=32,c=-10'

before execute line:7,a=8,b=32,c=-10

+ :

++ echo 'before execute line:9,a=8,b=32,c=-10'

before execute line:9,a=8,b=32,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:13,a=8,b=32,c=-10'

before execute line:13,a=8,b=32,c=-10

+ let a=a+2

++ echo 'before execute line:14,a=10,b=32,c=-10'

before execute line:14,a=10,b=32,c=-10

+ let 'b=b*2'

++ echo 'before execute line:15,a=10,b=64,c=-10'

before execute line:15,a=10,b=64,c=-10

+ let c=C-10

++ echo 'before execute line:7,a=10,b=64,c=-10'

before execute line:7,a=10,b=64,c=-10

+ :

++ echo 'before execute line:9,a=10,b=64,c=-10'

before execute line:9,a=10,b=64,c=-10

+ ((  a >= 10  ))

++ echo 'before execute line:11,a=10,b=64,c=-10'

before execute line:11,a=10,b=64,c=-10

+ break

6.在例子 17-1中:

415页第15行用正则表达式"$"匹配行首,应该是行尾巴.

在输入时需要主要>>CLOUD前不用留空格,在做分界的CLOUD前也不要有空格.

在例子17-1 htmlconver2.sh中:

#!/bin/bash

cat <<CLOUD

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transtitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<HTML>

   <HEAD>

      <TITLE>

      教授的信息

      </TITLE>

   </HEAD>

   <BODY>

      <TABLE>

CLOUD

awk 'BEGIN {FS=":";OFS="</TD><TD>"} sub(/^/,"<TR><TD>") sub(/$/,"</TD><TR>") {print  $1,$2,$3,$4}'

cat <<CLOUD

      </TABLE>

   </BODY>

</HTML>

CLOUD

运行结果:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transtitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<HTML>

   <HEAD>

      <TITLE>

      教授的信息

      </TITLE>

   </HEAD>

   <BODY>

      <TABLE>

<TR><TD>B Liu</TD><TD>Shanghai Jiaotong University</TD><TD>Shanghai</TD><TD>China</TD></TR>

<TR><TD>C Lin</TD><TD>University of Toronto</TD><TD>Toronto</TD><TD>Canada</
11e56
TD></TR>

<TR><TD>D Hou</TD><TD>Beijing University</TD><TD>Beijing</TD><TD>China</TD></TR>

<TR><TD>J Luo</TD><TD>Southeast University</TD><TD>Nanjing</TD><TD>China</TD></TR>

<TR><TD>Y Zhang</TD><TD>Victory University</TD><TD>Melbourne</TD><TD>Australia</TD></TR>

      </TABLE>

   </BODY>

</HTML>

注意到这里书中使用的不是sub,而是gsub:

#!/bin/bash

cat <<CLOUD

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transtitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<HTML>

   <HEAD>

      <TITLE>

      教授的信息

      </TITLE>

   </HEAD>

   <BODY>

      <TABLE>

CLOUD

awk 'BEGIN {FS=":";OFS="</TD><TD>"} gsub(/^/,"<TR><TD>") gsub(/$/,"</TD><TR>") {print  $1,$2,$3,$4}'

cat <<CLOUD

      </TABLE>

   </BODY>

</HTML>

CLOUD

运行结果:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transtitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<HTML>

   <HEAD>

      <TITLE>

      教授的信息

      </TITLE>

   </HEAD>

   <BODY>

      <TABLE>

<TR><TD>B<TR><TD> <TR><TD>L<TR><TD>i<TR><TD>u<TR><TD></TD><TD><TR><TD>S<TR><TD>h<TR><TD>a<TR><TD>n<TR><TD>g<TR><TD>h<TR><TD>a<TR><TD>i<TR><TD> <TR><TD>J<TR><TD>i<TR><TD>a<TR><TD>o<TR><TD>t<TR><TD>o<TR><TD>n<TR><TD>g<TR><TD> <TR><TD>U<TR><TD>n<TR><TD>i<TR><TD>v<TR><TD>e<TR><TD>r<TR><TD>s<TR><TD>i<TR><TD>t<TR><TD>y<TR><TD></TD><TD><TR><TD>S<TR><TD>h<TR><TD>a<TR><TD>n<TR><TD>g<TR><TD>h<TR><TD>a<TR><TD>i<TR><TD></TD><TD><TR><TD>C<TR><TD>h<TR><TD>i<TR><TD>n<TR><TD>a<TR><TD></TD><TR>

<TR><TD>C<TR><TD> <TR><TD>L<TR><TD>i<TR><TD>n<TR><TD></TD><TD><TR><TD>U<TR><TD>n<TR><TD>i<TR><TD>v<TR><TD>e<TR><TD>r<TR><TD>s<TR><TD>i<TR><TD>t<TR><TD>y<TR><TD> <TR><TD>o<TR><TD>f<TR><TD> <TR><TD>T<TR><TD>o<TR><TD>r<TR><TD>o<TR><TD>n<TR><TD>t<TR><TD>o<TR><TD></TD><TD><TR><TD>T<TR><TD>o<TR><TD>r<TR><TD>o<TR><TD>n<TR><TD>t<TR><TD>o<TR><TD></TD><TD><TR><TD>C<TR><TD>a<TR><TD>n<TR><TD>a<TR><TD>d<TR><TD>a<TR><TD></TD><TR>

<TR><TD>D<TR><TD> <TR><TD>H<TR><TD>o<TR><TD>u<TR><TD></TD><TD><TR><TD>B<TR><TD>e<TR><TD>i<TR><TD>j<TR><TD>i<TR><TD>n<TR><TD>g<TR><TD> <TR><TD>U<TR><TD>n<TR><TD>i<TR><TD>v<TR><TD>e<TR><TD>r<TR><TD>s<TR><TD>i<TR><TD>t<TR><TD>y<TR><TD></TD><TD><TR><TD>B<TR><TD>e<TR><TD>i<TR><TD>j<TR><TD>i<TR><TD>n<TR><TD>g<TR><TD></TD><TD><TR><TD>C<TR><TD>h<TR><TD>i<TR><TD>n<TR><TD>a<TR><TD></TD><TR>

<TR><TD>J<TR><TD> <TR><TD>L<TR><TD>u<TR><TD>o<TR><TD></TD><TD><TR><TD>S<TR><TD>o<TR><TD>u<TR><TD>t<TR><TD>h<TR><TD>e<TR><TD>a<TR><TD>s<TR><TD>t<TR><TD> <TR><TD>U<TR><TD>n<TR><TD>i<TR><TD>v<TR><TD>e<TR><TD>r<TR><TD>s<TR><TD>i<TR><TD>t<TR><TD>y<TR><TD></TD><TD><TR><TD>N<TR><TD>a<TR><TD>n<TR><TD>j<TR><TD>i<TR><TD>n<TR><TD>g<TR><TD></TD><TD><TR><TD>C<TR><TD>h<TR><TD>i<TR><TD>n<TR><TD>a<TR><TD></TD><TR>

<TR><TD>Y<TR><TD> <TR><TD>Z<TR><TD>h<TR><TD>a<TR><TD>n<TR><TD>g<TR><TD></TD><TD><TR><TD>V<TR><TD>i<TR><TD>c<TR><TD>t<TR><TD>o<TR><TD>r<TR><TD>y<TR><TD> <TR><TD>U<TR><TD>n<TR><TD>i<TR><TD>v<TR><TD>e<TR><TD>r<TR><TD>s<TR><TD>i<TR><TD>t<TR><TD>y<TR><TD></TD><TD><TR><TD>M<TR><TD>e<TR><TD>l<TR><TD>b<TR><TD>o<TR><TD>u<TR><TD>r<TR><TD>n<TR><TD>e<TR><TD></TD><TD><TR><TD>A<TR><TD>u<TR><TD>s<TR><TD>t<TR><TD>r<TR><TD>a<TR><TD>l<TR><TD>i<TR><TD>a<TR><TD></TD><TR>

      </TABLE>

   </BODY>

</HTML>

7.例子17-2的解析

#!/bin/bash

end=$1

cat $2

#tr -cs "[a-z][A-Z]" "[\012*]" |

#   tr A-Z a-z |

#       sort |

#          uniq -c |

#             sort -k1nr -k2 |

#                 head -n "$end"

运行./topn.sh 5 poem.txt

The Yangs: No silk thread can string these pearls;

           Dim now the tear-stains of those bygone years;

           A thousand bamboos grow before my window---

           Is each dappled and stained with tears?

Hawkes:    Yet silk preserves but ill the Naiad's tears:

           Each salty trace of them fast disapperars.

           Only the speckled bamboo stems that grow

           Outside the window still her tear-marks show.

==========================================

把非字母的部分变成回车

cat $2 |

tr -cs "[a-z][A-Z]" "[\012*]"

#   tr A-Z a-z |

#       sort |

#          uniq -c |

#             sort -k1nr -k2 |

#                 head -n "$end"

运行./topn.sh 5 poem.txt

The

Yangs

No

silk

thread

can

string

these

pearls

Dim

now

the

tear

stains

of

those

bygone

years

A

thousand

bamboos

grow

before

my

window

Is

each

dappled

and

stained

with

tears

Hawkes

Yet

silk

preserves

but

ill

the

Naiad

s

tears

Each

salty

trace

of

them

fast

disapperars

Only

the

speckled

bamboo

stems

that

grow

Outside

the

window

still

her

tear

marks

show

=============================

把大写改成小写

#!/bin/bash

end=$1

cat $2 |

tr -cs "[a-z][A-Z]" "[\012*]" |

   tr A-Z a-z

#       sort |

#          uniq -c |

#             sort -k1nr -k2 |

#                 head -n "$end"

运行./topn.sh 5 poem.txt

the

yangs

no

silk

thread

can

string

these

pearls

dim

now

the

tear

stains

of

those

bygone

years

a

thousand

bamboos

grow

before

my

window

is

each

dappled

and

stained

with

tears

hawkes

yet

silk

preserves

but

ill

the

naiad

s

tears

each

salty

trace

of

them

fast

disapperars

only

the

speckled

bamboo

stems

that

grow

outside

the

window

still

her

tear

marks

show

=========================

进行排序

#!/bin/bash

end=$1

cat $2 |

tr -cs "[a-z][A-Z]" "[\012*]" |

   tr A-Z a-z |

       sort

#          uniq -c |

#             sort -k1nr -k2 |

#                 head -n "$end"

运行:

a

and

bamboo

bamboos

before

but

bygone

can

dappled

dim

disapperars

each

each

fast

grow

grow

hawkes

her

ill

is

marks

my

naiad

no

now

of

of

only

outside

pearls

preserves

s

salty

show

silk

silk

speckled

stained

stains

stems

still

string

tear

tear

tears

tears

that

the

the

the

the

the

them

these

those

thousand

thread

trace

window

window

with

yangs

years

yet
=============================

计数

#!/bin/bash

end=$1

cat $2 |

tr -cs "[a-z][A-Z]" "[\012*]" |

   tr A-Z a-z |

       sort   |

          uniq -c

#             sort -k1nr -k2 |

#                 head -n "$end"

运行结果:

      1 a

      1 and

      1 bamboo

      1 bamboos

      1 before

      1 but

      1 bygone

      1 can

      1 dappled

      1 dim

      1 disapperars

      2 each

      1 fast

      2 grow

      1 hawkes

      1 her

      1 ill

      1 is

      1 marks

      1 my

      1 naiad

      1 no

      1 now

      2 of

      1 only

      1 outside

      1 pearls

      1 preserves

      1 s

      1 salty

      1 show

      2 silk

      1 speckled

      1 stained

      1 stains

      1 stems

      1 still

      1 string

      2 tear

      2 tears

      1 that

      5 the

      1 them

      1 these

      1 those

      1 thousand

      1 thread

      1 trace

      2 window

      1 with

      1 yangs

      1 years

      1 yet

=========================

按照第一列排序:

#!/bin/bash

end=$1

cat $2 |

tr -cs "[a-z][A-Z]" "[\012*]" |

   tr A-Z a-z |

       sort   |

          uniq -c |

             sort -k1nr -k2  //按照第一列数字(n)逆向(r)进行排序,按照第二列进行排序

#                 head -n "$end"

输出:

      5 the

      2 each

      2 grow

      2 of

      2 silk

      2 tear

      2 tears

      2 window

      1 a

      1 and

      1 bamboo

      1 bamboos

      1 before

      1 but

      1 bygone

      1 can

      1 dappled

      1 dim

      1 disapperars

      1 fast

      1 hawkes

      1 her

      1 ill

      1 is

      1 marks

      1 my

      1 naiad

      1 no

      1 now

      1 only

      1 outside

      1 pearls

      1 preserves

      1 s

      1 salty

      1 show

      1 speckled

      1 stained

      1 stains

      1 stems

      1 still

      1 string

      1 that

      1 them

      1 these

      1 those

      1 thousand

      1 thread

      1 trace

      1 with

      1 yangs

      1 years

      1 yet

====================================

列出前面几个:

#!/bin/bash

end=$1

cat $2 |

tr -cs "[a-z][A-Z]" "[\012*]" |

   tr A-Z a-z |

       sort   |

          uniq -c |

             sort -k1nr -k2 |

                 head -n "$end"

运行结果:

      5 the

      2 each

      2 grow

      2 of

      2 silk

*************************************************************

在例子17-5中最后缺少了一行:

#!/bin/bash

PIPS=6

MAX=1000

throw=1

one=0

two=0

three=0

four=0

five=0

six=0

count()

{

case "$1" in

0) let "one=one+1";;

1) let "two=two+1";;

2) let "three=three+1";;

3) let "four=four+1";;

4) let "five=five+1";;

5) let "six=six+1";;

esac

}

while [ "$throw" -le "$MAX" ]

do

  let "dice=RANDOM % $PIPS"

  count $dice

  let "throw=throw+1"

done

echo "The statistics results are as follows:"

echo "one=$one"

echo "two=$two"

echo "three=$three"

echo "four=$four"

echo "five=$five"

echo "six=$six"