contributed-scripts.html

一本完整的描述Unix Shell 编程的工具书的所有范例

><B
>Example A-15. <B
CLASS="COMMAND"
>fifo</B
>: Making daily backups, using named pipes</B
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><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# ==&#62; Script by James R. Van Zandt, and used here with his permission.
   3&nbsp;
   4&nbsp;# ==&#62; Comments added by author of this document.
   5&nbsp;
   6&nbsp;  
   7&nbsp;  HERE=`uname -n`    # ==&#62; hostname
   8&nbsp;  THERE=bilbo
   9&nbsp;  echo "starting remote backup to $THERE at `date +%r`"
  10&nbsp;  # ==&#62; `date +%r` returns time in 12-hour format, i.e. "08:08:34 PM".
  11&nbsp;  
  12&nbsp;  # make sure /pipe really is a pipe and not a plain file
  13&nbsp;  rm -rf /pipe
  14&nbsp;  mkfifo /pipe       # ==&#62; Create a "named pipe", named "/pipe".
  15&nbsp;  
  16&nbsp;  # ==&#62; 'su xyz' runs commands as user "xyz".
  17&nbsp;  # ==&#62; 'ssh' invokes secure shell (remote login client).
  18&nbsp;  su xyz -c "ssh $THERE \"cat &#62;/home/xyz/backup/${HERE}-daily.tar.gz\" &#60; /pipe"&#38;
  19&nbsp;  cd /
  20&nbsp;  tar -czf - bin boot dev etc home info lib man root sbin share usr var &#62;/pipe
  21&nbsp;  # ==&#62; Uses named pipe, /pipe, to communicate between processes:
  22&nbsp;  # ==&#62; 'tar/gzip' writes to /pipe and 'ssh' reads from /pipe.
  23&nbsp;
  24&nbsp;  # ==&#62; The end result is this backs up the main directories, from / on down.
  25&nbsp;
  26&nbsp;  # ==&#62;  What are the advantages of a "named pipe" in this situation,
  27&nbsp;  # ==&#62;+ as opposed to an "anonymous pipe", with |?
  28&nbsp;  # ==&#62;  Will an anonymous pipe even work here?
  29&nbsp;
  30&nbsp;
  31&nbsp;  exit 0</PRE
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><P
>+</P
><P
>St閜hane Chazelas contributed the following script to
      demonstrate that generating prime numbers does not require
      arrays.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="PRIMES"
></A
><P
><B
>Example A-16. Generating prime numbers using the modulo operator</B
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><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
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><P
>+</P
><P
>This is Rick Boivie's revision of Jordi Sanfeliu's
      <I
CLASS="EMPHASIS"
>tree</I
> script.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="TREE"
></A
><P
><B
>Example A-17. <B
CLASS="COMMAND"
>tree</B
>: Displaying a directory tree</B
></P
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><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
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><HR></DIV
><P
>Noah Friedman gave permission to use his <I
CLASS="EMPHASIS"
>string
      function</I
> script, which essentially reproduces some of the
      C-library string manipulation functions.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="STRING"
></A
><P
><B
>Example A-18. <B
CLASS="COMMAND"
>string functions</B
>: C-like string functions</B
></P
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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