contributed-scripts.html

来自「BASH Shell 编程 经典教程 《高级SHELL脚本编程》中文版」· HTML 代码 · 共 2,144 行 · 第 1/5 页

  6   
  7   HERE=`uname -n`    # ==> hostname
  8   THERE=bilbo
  9   echo "starting remote backup to $THERE at `date +%r`"
 10   # ==> `date +%r` returns time in 12-hour format, i.e. "08:08:34 PM".
 11   
 12   # make sure /pipe really is a pipe and not a plain file
 13   rm -rf /pipe
 14   mkfifo /pipe       # ==> Create a "named pipe", named "/pipe".
 15   
 16   # ==> 'su xyz' runs commands as user "xyz".
 17   # ==> 'ssh' invokes secure shell (remote login client).
 18   su xyz -c "ssh $THERE \"cat >/home/xyz/backup/${HERE}-daily.tar.gz\" < /pipe"&
 19   cd /
 20   tar -czf - bin boot dev etc home info lib man root sbin share usr var >/pipe
 21   # ==> Uses named pipe, /pipe, to communicate between processes:
 22   # ==> 'tar/gzip' writes to /pipe and 'ssh' reads from /pipe.
 23 
 24   # ==> The end result is this backs up the main directories, from / on down.
 25 
 26   # ==>  What are the advantages of a "named pipe" in this situation,
 27   # ==>+ as opposed to an "anonymous pipe", with |?
 28   # ==>  Will an anonymous pipe even work here?
 29 
 30 
 31&nbsp;  exit 0</PRE
></FONT
></TD
></TR
></TABLE
><HR></DIV
><P
>+</P
><P
>Stephane Chazelas捐献了这个脚本, 用来展示如何不使用数组来产生素数</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="PRIMES"
></A
><P
><B
>例子 A-16. 使用模操作符来产生素数</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="PROGRAMLISTING"
>  1&nbsp;#!/bin/bash
  2&nbsp;# primes.sh: Generate prime numbers, without using arrays.
  3&nbsp;# Script contributed by Stephane Chazelas.
  4&nbsp;
  5&nbsp;#  This does *not* use the classic "Sieve of Eratosthenes" algorithm,
  6&nbsp;#+ but instead uses the more intuitive method of testing each candidate number
  7&nbsp;#+ for factors (divisors), using the "%" modulo operator.
  8&nbsp;
  9&nbsp;
 10&nbsp;LIMIT=1000                    # Primes 2 - 1000
 11&nbsp;
 12&nbsp;Primes()
 13&nbsp;{
 14&nbsp; (( n = $1 + 1 ))             # Bump to next integer.
 15&nbsp; shift                        # Next parameter in list.
 16&nbsp;#  echo "_n=$n i=$i_"
 17&nbsp; 
 18&nbsp; if (( n == LIMIT ))
 19&nbsp; then echo $*
 20&nbsp; return
 21&nbsp; fi
 22&nbsp;
 23&nbsp; for i; do                    # "i" gets set to "@", previous values of $n.
 24&nbsp;#   echo "-n=$n i=$i-"
 25&nbsp;   (( i * i &#62; n )) &#38;&#38; break   # Optimization.
 26&nbsp;   (( n % i )) &#38;&#38; continue    # Sift out non-primes using modulo operator.
 27&nbsp;   Primes $n $@               # Recursion inside loop.
 28&nbsp;   return
 29&nbsp;   done
 30&nbsp;
 31&nbsp;   Primes $n $@ $n            # Recursion outside loop.
 32&nbsp;                              # Successively accumulate positional parameters.
 33&nbsp;                              # "$@" is the accumulating list of primes.
 34&nbsp;}
 35&nbsp;
 36&nbsp;Primes 1
 37&nbsp;
 38&nbsp;exit 0
 39&nbsp;
 40&nbsp;#  Uncomment lines 16 and 24 to help figure out what is going on.
 41&nbsp;
 42&nbsp;#  Compare the speed of this algorithm for generating primes
 43&nbsp;#+ with the Sieve of Eratosthenes (ex68.sh).
 44&nbsp;
 45&nbsp;#  Exercise: Rewrite this script without recursion, for faster execution.</PRE
></FONT
></TD
></TR
></TABLE
><HR></DIV
><P
>+</P
><P
>这是Jordi Sanfeliu的<EM
>tree</EM
>脚本的升级版, 由Rick Boivie编写. </P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="TREE"
></A
><P
><B
>例子 A-17. <B
CLASS="COMMAND"
>tree</B
>: 显示目录树</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="PROGRAMLISTING"
>  1&nbsp;#!/bin/bash
  2&nbsp;# tree.sh
  3&nbsp;
  4&nbsp;#  Written by Rick Boivie.
  5&nbsp;#  Used with permission.
  6&nbsp;#  This is a revised and simplified version of a script
  7&nbsp;#+ by Jordi Sanfeliu (and patched by Ian Kjos).
  8&nbsp;#  This script replaces the earlier version used in
  9&nbsp;#+ previous releases of the Advanced Bash Scripting Guide.
 10&nbsp;
 11&nbsp;# ==&#62; Comments added by the author of this document.
 12&nbsp;
 13&nbsp;
 14&nbsp;search () {
 15&nbsp;for dir in `echo *`
 16&nbsp;#  ==&#62; `echo *` lists all the files in current working directory,
 17&nbsp;#+ ==&#62; without line breaks.
 18&nbsp;#  ==&#62; Similar effect to for dir in *
 19&nbsp;#  ==&#62; but "dir in `echo *`" will not handle filenames with blanks.
 20&nbsp;do
 21&nbsp;  if [ -d "$dir" ] ; then # ==&#62; If it is a directory (-d)...
 22&nbsp;  zz=0                    # ==&#62; Temp variable, keeping track of directory level.
 23&nbsp;  while [ $zz != $1 ]     # Keep track of inner nested loop.
 24&nbsp;    do
 25&nbsp;      echo -n "| "        # ==&#62; Display vertical connector symbol,
 26&nbsp;                          # ==&#62; with 2 spaces &#38; no line feed in order to indent.
 27&nbsp;      zz=`expr $zz + 1`   # ==&#62; Increment zz.
 28&nbsp;    done
 29&nbsp;
 30&nbsp;    if [ -L "$dir" ] ; then # ==&#62; If directory is a symbolic link...
 31&nbsp;      echo "+---$dir" `ls -l $dir | sed 's/^.*'$dir' //'`
 32&nbsp;      # ==&#62; Display horiz. connector and list directory name, but...
 33&nbsp;      # ==&#62; delete date/time part of long listing.
 34&nbsp;    else
 35&nbsp;      echo "+---$dir"       # ==&#62; Display horizontal connector symbol...
 36&nbsp;      # ==&#62; and print directory name.
 37&nbsp;      numdirs=`expr $numdirs + 1` # ==&#62; Increment directory count.
 38&nbsp;      if cd "$dir" ; then         # ==&#62; If can move to subdirectory...
 39&nbsp;        search `expr $1 + 1`      # with recursion ;-)
 40&nbsp;        # ==&#62; Function calls itself.
 41&nbsp;        cd ..
 42&nbsp;      fi
 43&nbsp;    fi
 44&nbsp;  fi
 45&nbsp;done
 46&nbsp;}
 47&nbsp;
 48&nbsp;if [ $# != 0 ] ; then
 49&nbsp;  cd $1 # move to indicated directory.
 50&nbsp;  #else # stay in current directory
 51&nbsp;fi
 52&nbsp;
 53&nbsp;echo "Initial directory = `pwd`"
 54&nbsp;numdirs=0
 55&nbsp;
 56&nbsp;search 0
 57&nbsp;echo "Total directories = $numdirs"
 58&nbsp;
 59&nbsp;exit 0</PRE
></FONT
></TD
></TR
></TABLE
><HR></DIV
><P
>经过Noah Friedman的授权, 他的<EM
>string
			function</EM
>脚本可以在本书中使用, 
		这个脚本本质上就是复制了一些C库的字符串操作函数. 
      </P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="STRING"
></A
><P
><B
>例子 A-18. <B
CLASS="COMMAND"
>string functions</B
>: C风格的字符串函数</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="PROGRAMLISTING"
>  1&nbsp;#!/bin/bash
  2&nbsp;
  3&nbsp;# string.bash --- bash emulation of string(3) library routines
  4&nbsp;# Author: Noah Friedman &#60;[e-mail]&#62;
  5&nbsp;# ==&#62;     Used with his kind permission in this document.
  6&nbsp;# Created: 1992-07-01
  7&nbsp;# Last modified: 1993-09-29
  8&nbsp;# Public domain
  9&nbsp;
 10&nbsp;# Conversion to bash v2 syntax done by Chet Ramey
 11&nbsp;
 12&nbsp;# Commentary:
 13&nbsp;# Code:
 14&nbsp;
 15&nbsp;#:docstring strcat:
 16&nbsp;# Usage: strcat s1 s2
 17&nbsp;#
 18&nbsp;# Strcat appends the value of variable s2 to variable s1. 
 19&nbsp;#
 20&nbsp;# Example:
 21&nbsp;#    a="foo"
 22&nbsp;#    b="bar"
 23&nbsp;#    strcat a b
 24&nbsp;#    echo $a
 25&nbsp;#    =&#62; foobar
 26&nbsp;#
 27&nbsp;#:end docstring:
 28&nbsp;
 29&nbsp;###;;;autoload   ==&#62; Autoloading of function commented out.
 30&nbsp;function strcat ()
 31&nbsp;{
 32&nbsp;    local s1_val s2_val
 33&nbsp;
 34&nbsp;    s1_val=${!1}                        # indirect variable expansion
 35&nbsp;    s2_val=${!2}
 36&nbsp;    eval "$1"=\'"${s1_val}${s2_val}"\'
 37&nbsp;    # ==&#62; eval $1='${s1_val}${s2_val}' avoids problems,
 38&nbsp;    # ==&#62; if one of the variables contains a single quote.
 39&nbsp;}
 40&nbsp;
 41&nbsp;#:docstring strncat:
 42&nbsp;# Usage: strncat s1 s2 $n
 43&nbsp;# 
 44&nbsp;# Line strcat, but strncat appends a maximum of n characters from the value
 45&nbsp;# of variable s2.  It copies fewer if the value of variabl s2 is shorter
 46&nbsp;# than n characters.  Echoes result on stdout.
 47&nbsp;#
 48&nbsp;# Example:
 49&nbsp;#    a=foo
 50&nbsp;#    b=barbaz
 51&nbsp;#    strncat a b 3
 52&nbsp;#    echo $a
 53&nbsp;#    =&#62; foobar
 54&nbsp;#
 55&nbsp;#:end docstring:
 56&nbsp;
 57&nbsp;###;;;autoload
 58&nbsp;function strncat ()
 59&nbsp;{
 60&nbsp;    local s1="$1"
 61&nbsp;    local s2="$2"
 62&nbsp;    local -i n="$3"
 63&nbsp;    local s1_val s2_val
 64&nbsp;
 65&nbsp;    s1_val=${!s1}                       # ==&#62; indirect variable expansion
 66&nbsp;    s2_val=${!s2}
 67&nbsp;
 68&nbsp;    if [ ${#s2_val} -gt ${n} ]; then
 69&nbsp;       s2_val=${s2_val:0:$n}            # ==&#62; substring extraction
 70&nbsp;    fi
 71&nbsp;
 72&nbsp;    eval "$s1"=\'"${s1_val}${s2_val}"\'
 73&nbsp;    # ==&#62; eval $1='${s1_val}${s2_val}' avoids problems,
 74&nbsp;    # ==&#62; if one of the variables contains a single quote.
 75&nbsp;}
 76&nbsp;
 77&nbsp;#:docstring strcmp:
 78&nbsp;# Usage: strcmp $s1 $s2
 79&nbsp;#
 80&nbsp;# Strcmp compares its arguments and returns an integer less than, equal to,
 81&nbsp;# or greater than zero, depending on whether string s1 is lexicographically
 82&nbsp;# less than, equal to, or greater than string s2.
 83&nbsp;#:end docstring:
 84&nbsp;
 85&nbsp;###;;;autoload
 86&nbsp;function strcmp ()
 87&nbsp;{
 88&nbsp;    [ "$1" = "$2" ] &#38;&#38; return 0
 89&nbsp;
 90&nbsp;    [ "${1}" '&#60;' "${2}" ] &#62; /dev/null &#38;&#38; return -1
 91&nbsp;
 92&nbsp;    return 1
 93&nbsp;}
 94&nbsp;
 95&nbsp;#:docstring strncmp:
 96&nbsp;# Usage: strncmp $s1 $s2 $n
 97&nbsp;# 
 98&nbsp;# Like strcmp, but makes the comparison by examining a maximum of n
 99&nbsp;# characters (n less than or equal to zero yields equality).
100&nbsp;#:end docstring:
101&nbsp;
102&nbsp;###;;;autoload
103&nbsp;function strncmp ()
104&nbsp;{
105&nbsp;    if [ -z "${3}" -o "${3}" -le "0" ]; then
106&nbsp;       return 0
107&nbsp;    fi
108&nbsp;   
109&nbsp;    if [ ${3} -ge ${#1} -a ${3} -ge ${#2} ]; then
110&nbsp;       strcmp "$1" "$2"
111&nbsp;       return $?
112&nbsp;    else
113&nbsp;       s1=${1:0:$3}
114&nbsp;       s2=${2:0:$3}
115&nbsp;       strcmp $s1 $s2
116&nbsp;       return $?
117&nbsp;    fi
118&nbsp;}
119&nbsp;
120&nbsp;#:docstring strlen:
121&nbsp;# Usage: strlen s
122&nbsp;#
123&nbsp;# Strlen returns the number of characters in string literal s.
124&nbsp;#:end docstring:
125&nbsp;
126&nbsp;###;;;autoload
127&nbsp;function strlen ()
128&nbsp;{
129&nbsp;    eval echo "\${#${1}}"
130&nbsp;    # ==&#62; Returns the length of the value of the variable
131&nbsp;    # ==&#62; whose name is passed as an argument.
132&nbsp;}
133&nbsp;
134&nbsp;#:docstring strspn:
135&nbsp;# Usage: strspn $s1 $s2
136&nbsp;# 
137&nbsp;# Strspn returns the length of the maximum initial segment of string s1,
138&nbsp;# which consists entirely of characters from string s2.
139&nbsp;#:end docstring:
140&nbsp;
141&nbsp;###;;;autoload
142&nbsp;function strspn ()
143&nbsp;{
144&nbsp;    # Unsetting IFS allows whitespace to be handled as normal chars. 
145&nbsp;    local IFS=
146&nbsp;    local result="${1%%[!${2}]*}"
147&nbsp; 
148&nbsp;    echo ${#result}
149&nbsp;}
150&nbsp;
151&nbsp;#:docstring strcspn:
152&nbsp;# Usage: strcspn $s1 $s2
153&nbsp;#
154&nbsp;# Strcspn returns the length of the maximum initial segment of string s1,
155&nbsp;# which consists entirely of characters not from string s2.
156&nbsp;#:end docstring:
157&nbsp;
158&nbsp;###;;;autoload
159&nbsp;function strcspn ()
160&nbsp;{
161&nbsp;    # Unsetting IFS allows whitspace to be handled as normal chars. 
162&nbsp;    local IFS=
163&nbsp;    local result="${1%%[${2}]*}"
164&nbsp; 
165&nbsp;    echo ${#result}
166&nbsp;}
167&nbsp;
168&nbsp;#:docstring strstr:
169&nbsp;# Usage: strstr s1 s2
170&nbsp;# 
171&nbsp;# Strstr echoes a substring starting at the first occurrence of string s2 in
172&nbsp;# string s1, or nothing if s2 does not occur in the string.  If s2 points to
173&nbsp;# a string of zero length, strstr echoes s1.
174&nbsp;#:end docstring:
175&nbsp;
176&nbsp;###;;;autoload
177&nbsp;function strstr ()
178&nbsp;{
179&nbsp;    # if s2 points to a string of zero length, strstr echoes s1
180&nbsp;    [ ${#2} -eq 0 ] &#38;&#38; { echo "$1" ; return 0; }
181&nbsp;
182&nbsp;    # strstr echoes nothing if s2 does not occur in s1
183&nbsp;    case "$1" in
184&nbsp;    *$2*) ;;
185&nbsp;    *) return 1;;
186&nbsp;    esac
187&nbsp;
188&nbsp;    # use the pattern matching code to strip off the match and everything
189&nbsp;    # following it
190&nbsp;    first=${1/$2*/}
191&nbsp;
192&nbsp;    # then strip off the first unmatched portion of the string
193&nbsp;    echo "${1##$first}"
194&nbsp;}
195&nbsp;
196&nbsp;#:docstring strtok:
197&nbsp;# Usage: strtok s1 s2
198&nbsp;#
199&nbsp;# Strtok considers the string s1 to consist of a sequence of zero or more
200&nbsp;# text tokens separated by spans of one or more characters from the
201&nbsp;# separator string s2.  The first call (with a non-empty string s1
202&nbsp;# specified) echoes a string consisting of the first token on stdout. The
203&nbsp