contributed-scripts.html

Shall高级编程

   9 
  10 
  11 MATRIX="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
  12 # ==> Password will consist of alphanumeric characters.
  13 LENGTH="8"
  14 # ==> May change 'LENGTH' for longer password.
  15 
  16 
  17 while [ "${n:=1}" -le "$LENGTH" ]
  18 # ==> Recall that := is "default substitution" operator.
  19 # ==> So, if 'n' has not been initialized, set it to 1.
  20 do
  21 	PASS="$PASS${MATRIX:$(($RANDOM%${#MATRIX})):1}"
  22 	# ==> Very clever, but tricky.
  23 
  24 	# ==> Starting from the innermost nesting...
  25 	# ==> ${#MATRIX} returns length of array MATRIX.
  26 
  27 	# ==> $RANDOM%${#MATRIX} returns random number between 1
  28 	# ==> and [length of MATRIX] - 1.
  29 
  30 	# ==> ${MATRIX:$(($RANDOM%${#MATRIX})):1}
  31 	# ==> returns expansion of MATRIX at random position, by length 1. 
  32 	# ==> See {var:pos:len} parameter substitution in Chapter 9.
  33 	# ==> and the associated examples.
  34 
  35 	# ==> PASS=... simply pastes this result onto previous PASS (concatenation).
  36 
  37 	# ==> To visualize this more clearly, uncomment the following line
  38 	#                 echo "$PASS"
  39 	# ==> to see PASS being built up,
  40 	# ==> one character at a time, each iteration of the loop.
  41 
  42 	let n+=1
  43 	# ==> Increment 'n' for next pass.
  44 done
  45 
  46 echo "$PASS"      # ==> Or, redirect to a file, as desired.
  47 
  48&nbsp;exit 0</PRE
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><HR></DIV
><P
>+</P
><P
><A
NAME="ZFIFO"
></A
>James R. Van Zandt contributed this script
      which uses named pipes and, in his words, <SPAN
CLASS="QUOTE"
>"really exercises
      quoting and escaping."</SPAN
></P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="FIFO"
></A
><P
><B
>Example A-15. <I
CLASS="FIRSTTERM"
>fifo</I
>: Making daily backups, using
      named pipes</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><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;  # ==&#62;  Is it necessary to delete the pipe before exiting the script?
  31&nbsp;  # ==&#62;  How could that be done?
  32&nbsp;
  33&nbsp;
  34&nbsp;  exit 0</PRE
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><HR></DIV
><P
>+</P
><P
><A
NAME="PRIMES1"
></A
></P
><P
>St閜hane Chazelas used the following script to
      demonstrate generating prime numbers without arrays.</P
><P
><A
NAME="PRIMES00"
></A
></P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="PRIMES"
></A
><P
><B
>Example A-16. Generating prime numbers using the modulo operator</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><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 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" 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 $?  # Pipe output of the script to 'fmt' for prettier printing.
  39&nbsp;
  40&nbsp;#  Uncomment lines 16 and 24 to help figure out what is going on.
  41&nbsp;
  42&nbsp;#  Compare the speed of this algorithm for generating primes
  43&nbsp;#+ with the Sieve of Eratosthenes (ex68.sh).
  44&nbsp;
  45&nbsp;
  46&nbsp;#  Exercise: Rewrite this script without recursion, for faster execution.</PRE
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><HR></DIV
><P
>+</P
><P
>Rick Boivie's revision of Jordi Sanfeliu's
      <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>tree</I
></SPAN
> script.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="TREE"
></A
><P
><B
>Example A-17. <I
CLASS="FIRSTTERM"
>tree</I
>: Displaying a directory tree</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# tree.sh
   3&nbsp;
   4&nbsp;#  Written by Rick Boivie.
   5&nbsp;#  Used with permission.
   6&nbsp;#  This is a revised and simplified version of a script
   7&nbsp;#+ by Jordi Sanfeliu (and patched by Ian Kjos).
   8&nbsp;#  This script replaces the earlier version used in
   9&nbsp;#+ previous releases of the Advanced Bash Scripting Guide.
  10&nbsp;
  11&nbsp;# ==&#62; Comments added by the author of this document.
  12&nbsp;
  13&nbsp;
  14&nbsp;search () {
  15&nbsp;for dir in `echo *`
  16&nbsp;#  ==&#62; `echo *` lists all the files in current working directory,
  17&nbsp;#+ ==&#62; without line breaks.
  18&nbsp;#  ==&#62; Similar effect to for dir in *
  19&nbsp;#  ==&#62; but "dir in `echo *`" will not handle filenames with blanks.
  20&nbsp;do
  21&nbsp;  if [ -d "$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
>Patsie's version of a directory <I
CLASS="FIRSTTERM"
>tree</I
>
      script.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="TREE2"
></A
><P
><B
>Example A-18. <I
CLASS="FIRSTTERM"
>tree2</I
>: Alternate directory tree script</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# tree2.sh
   3&nbsp;
   4&nbsp;# Lightly modified/reformatted by ABS Guide author.
   5&nbsp;# Included in ABS Guide with permission of script author (thanks!).
   6&nbsp;
   7&nbsp;## Recursive file/dirsize checking script, by Patsie
   8&nbsp;##
   9&nbsp;## This script builds a list of files/directories and their size (du -akx)
  10&nbsp;## and processes this list to a human readable tree shape
  11&nbsp;## The 'du -akx' is only as good as the permissions the owner has.
  12&nbsp;## So preferably run as root* to get the best results, or use only on
  13&nbsp;## directories for which you have read permissions. Anything you can't
  14&nbsp;## read is not in the list.
  15&nbsp;
  16&nbsp;#* ABS Guide author advises caution when running scripts as root!
  17&nbsp;
  18&nbsp;
  19&nbsp;##########  THIS IS CONFIGURABLE  ##########
  20&nbsp;
  21&nbsp;TOP=5                   # Top 5 biggest (sub)directories.
  22&nbsp;MAXRECURS=5             # Max 5 subdirectories/recursions deep.
  23&nbsp;E_BL=80                 # Blank line already returned.
  24&nbsp;E_DIR=81                # Directory not specified.
  25&nbsp;
  26&nbsp;
  27&nbsp;##########  DON'T CHANGE ANYTHING BELOW THIS LINE  ##########
  28&nbsp;
  29&nbsp;PID=$$                            # Our own process ID.
  30&nbsp;SELF=`basename $0`                # Our own program name.
  31&nbsp;TMP="/tmp/${SELF}.${PID}.tmp"     # Temporary 'du' result.
  32&nbsp;
  33&nbsp;# Convert number to dotted thousand.
  34&nbsp;function dot { echo "            $*" |
  35&nbsp;               sed -e :a -e 's/\(.*[0-9]\)\([0-9]\{3\}\)/\1,\2/;ta' |
  36&nbsp;               tail -c 12; }
  37&nbsp;
  38&nbsp;# Usage: tree &#60;recursion&#62; &#60;indent prefix&#62; &#60;min size&#62; &#60;directory&#62;
  39&nbsp;function tree {
  40&nbsp;  recurs="$1"           # How deep nested are we?
  41&nbsp;  prefix="$2"           # What do we display before file/dirname?
  42&nbsp;  minsize="$3"          # What is the minumum file/dirsize?
  43&nbsp;  dirname="$4"          # Which directory are we checking?
  44&nbsp;
  45&nbsp;# Get ($TOP) biggest subdirs/subfiles from TMP file.
  46&nbsp;  LIST=`egrep "[[:space:]]${dirname}/[^/]*$" "$TMP" |
  47&nbsp;        awk '{if($1&#62;'$minsize') print;}' | sort -nr | head -$TOP`
  48&nbsp;  [ -z "$LIST" ] &#38;&#38; return        # Empty list, then go back.
  49&nbsp;
  50&nbsp;  cnt=0
  51&nbsp;  num=`echo "$LIST" | wc -l`      # How many entries in the list.
  52&nbsp;
  53&nbsp;  ## Main loop
  54&nbsp;  echo "$LIST" | while read size name; do
  55&nbsp;    ((cnt+=1))		          # Count entry number.
  56&nbsp;    bname=`basename "$name"`      # We only need a basename of the entry.
  57&nbsp;    [ -d "$name" ] &#38;&#38; bname="$bname/"
  58&nbsp;                                  # If it's a directory, append a slash.
  59&nbsp;    echo "`dot $size`$prefix +-$bname"
  60&nbsp;                                  # Display the result.
  61&nbsp;    #  Call ourself recursively if it's a directory
  62&nbsp;    #+ and we're not nested too deep ($MAXRECURS).
  63&nbsp;    #  The recursion goes up: $((recurs+1))
  64&nbsp;    #  The prefix gets a space if it's the last entry,
  65&nbsp;    #+ or a pipe if there are more entries.
  66&nbsp;    #  The minimum file/dirsize becomes
  67&nbsp;    #+ a tenth of his parent: $((size/10)).
  68&nbsp;    # Last argument is the full directory name to check.
  69&nbsp;    if [ -d "$name" -a $recurs -lt $MAXRECURS ]; then
  70&nbsp;      [ $cnt -lt $num ] \
  71&nbsp;        || (tree $((recurs+1)) "$prefix  " $((size/10)) "$name") \
  72&nbsp;        &#38;&#38; (tree $((recurs+1)) "$prefix |" $((size/10)) "$name")
  73&nbsp;    fi
  74&nbsp;  done
  75&nbsp;
  76&nbsp;  [ $? -eq 0 ] &#38;&#38; echo "           $prefix"
  77&nbsp;  # Every time we jump back add a 'blank' line.
  78&nbsp;  return $E_BL
  79&nbsp;  # We return 80 to tell we added a blank line already.
  80&nbsp;}
  81&nbsp;
  82&nbsp;###                ###
  83&nbsp;###  main program  ###
  84&nbsp;###                ###
  85&nbsp;
  86&nbsp;rootdir="$@"
  87&nbsp;[ -d "$rootdir" ] ||
  88&nbsp;  { echo "$SELF: Usage: $SELF &#60;directory&#62;" &#62;&#38;2; exit $E_DIR; }
  89&nbsp;  # We should be called with a directory name.
  90&nbsp;
  91&nbsp;echo "Building inventory list, please wait ..."
  92&nbsp;     # Show "please wait" message.
  93&nbsp;du -akx "$rootdir" 1&#62;"$TMP" 2&#62;/dev/null
  94&nbsp;     # Build a temporary list of all files/dirs and their size