communications.html

Shall高级编程

  27 # -t: reserve time
  28 # -v: verbose
  29 
  30 OPTS="-rtv --delete-excluded --delete-after --partial"
  31 
  32 # rsync include pattern
  33 # Leading slash causes absolute path name match.
  34 INCLUDE=(
  35     "/4/i386/kde-i18n-Chinese*" 
  36 #   ^                         ^
  37 # Quoting is necessary to prevent globbing.
  38 ) 
  39 
  40 
  41 # rsync exclude pattern
  42 # Temporarily comment out unwanted pkgs using "#" . . .
  43 EXCLUDE=(
  44     /1
  45     /2
  46     /3
  47     /testing
  48     /4/SRPMS
  49     /4/ppc
  50     /4/x86_64
  51     /4/i386/debug
  52    "/4/i386/kde-i18n-*"
  53    "/4/i386/openoffice.org-langpack-*"
  54    "/4/i386/*i586.rpm"
  55    "/4/i386/GFS-*"
  56    "/4/i386/cman-*"
  57    "/4/i386/dlm-*"
  58    "/4/i386/gnbd-*"
  59    "/4/i386/kernel-smp*"
  60 #  "/4/i386/kernel-xen*" 
  61 #  "/4/i386/xen-*" 
  62 )
  63 
  64 
  65 init () {
  66     # Let pipe command return possible rsync error, e.g., stalled network.
  67     set -o pipefail                  # Newly introduced in Bash, version 3.
  68 
  69     TMP=${TMPDIR:-/tmp}/${0##*/}.$$  # Store refined download list.
  70     trap "{
  71         rm -f $TMP 2>/dev/null
  72     }" EXIT                          # Clear temporary file on exit.
  73 }
  74 
  75 
  76 check_pid () {
  77 # Check if process exists.
  78     if [ -s "$PID_FILE" ]; then
  79         echo "PID file exists. Checking ..."
  80         PID=$(/bin/egrep -o "^[[:digit:]]+" $PID_FILE)
  81         if /bin/ps --pid $PID &>/dev/null; then
  82             echo "Process $PID found. ${0##*/} seems to be running!"
  83            /usr/bin/logger -t ${0##*/} \
  84                  "Process $PID found. ${0##*/} seems to be running!"
  85             exit $E_RETURN
  86         fi
  87         echo "Process $PID not found. Start new process . . ."
  88     fi
  89 }
  90 
  91 
  92 #  Set overall file update range starting from root or $URL,
  93 #+ according to above patterns.
  94 set_range () {
  95     include=
  96     exclude=
  97     for p in "${INCLUDE[@]}"; do
  98         include="$include --include \"$p\""
  99     done
 100 
 101     for p in "${EXCLUDE[@]}"; do
 102         exclude="$exclude --exclude \"$p\""
 103     done
 104 }
 105 
 106 
 107 # Retrieve and refine rsync update list.
 108 get_list () {
 109     echo $$ > $PID_FILE || {
 110         echo "Can't write to pid file $PID_FILE"
 111         exit $E_RETURN
 112     }
 113 
 114     echo -n "Retrieving and refining update list . . ."
 115 
 116     # Retrieve list -- 'eval' is needed to run rsync as a single command.
 117     # $3 and $4 is the date and time of file creation.
 118     # $5 is the full package name.
 119     previous=
 120     pre_file=
 121     pre_date=0
 122     eval /bin/nice /usr/bin/rsync \
 123         -r $include $exclude $URL | \
 124         egrep '^dr.x|^-r' | \
 125         awk '{print $3, $4, $5}' | \
 126         sort -k3 | \
 127         { while read line; do
 128             # Get seconds since epoch, to filter out obsolete pkgs.
 129             cur_date=$(date -d "$(echo $line | awk '{print $1, $2}')" +%s)
 130             #  echo $cur_date
 131 
 132             # Get file name.
 133             cur_file=$(echo $line | awk '{print $3}')
 134             #  echo $cur_file
 135 
 136             # Get rpm pkg name from file name, if possible.
 137             if [[ $cur_file == *rpm ]]; then
 138                 pkg_name=$(echo $cur_file | sed -r -e \
 139                     's/(^([^_-]+[_-])+)[[:digit:]]+\..*[_-].*$/\1/')
 140             else
 141                 pkg_name=
 142             fi
 143             # echo $pkg_name
 144 
 145             if [ -z "$pkg_name" ]; then   #  If not a rpm file,
 146                 echo $cur_file >> $TMP    #+ then append to download list.
 147             elif [ "$pkg_name" != "$previous" ]; then   # A new pkg found.
 148                 echo $pre_file >> $TMP                  # Output latest file.
 149                 previous=$pkg_name                      # Save current.
 150                 pre_date=$cur_date
 151                 pre_file=$cur_file
 152             elif [ "$cur_date" -gt "$pre_date" ]; then
 153                                                 #  If same pkg, but newer,
 154                 pre_date=$cur_date              #+ then update latest pointer.
 155                 pre_file=$cur_file
 156             fi
 157             done
 158             echo $pre_file >> $TMP              #  TMP contains ALL
 159                                                 #+ of refined list now.
 160             # echo "subshell=$BASH_SUBSHELL"
 161 
 162     }       # Bracket required here to let final "echo $pre_file >> $TMP" 
 163             # Remained in the same subshell ( 1 ) with the entire loop.
 164 
 165     RET=$?  # Get return code of the pipe command.
 166 
 167     [ "$RET" -ne 0 ] && {
 168         echo "List retrieving failed with code $RET"
 169         exit $E_RETURN
 170     }
 171 
 172     echo "done"; echo
 173 }
 174 
 175 # Real rsync download part.
 176 get_file () {
 177 
 178     echo "Downloading..."
 179     /bin/nice /usr/bin/rsync \
 180         $OPTS \
 181         --filter "merge,+/ $TMP" \
 182         --exclude '*'  \
 183         $URL $DEST     \
 184         | /usr/bin/tee $LOG
 185 
 186     RET=$?
 187 
 188    #  --filter merge,+/ is crucial for the intention. 
 189    #  + modifier means include and / means absolute path.
 190    #  Then sorted list in $TMP will contain ascending dir name and 
 191    #+ prevent the following --exclude '*' from "shortcutting the circuit." 
 192 
 193     echo "Done"
 194 
 195     rm -f $PID_FILE 2>/dev/null
 196 
 197     return $RET
 198 }
 199 
 200 # -------
 201 # Main
 202 init
 203 check_pid
 204 set_range
 205 get_list
 206 get_file
 207 RET=$?
 208 # -------
 209 
 210 if [ "$RET" -eq 0 ]; then
 211     /usr/bin/logger -t ${0##*/} "Fedora update mirrored successfully."
 212 else
 213     /usr/bin/logger -t ${0##*/} \
 214     "Fedora update mirrored with failure code: $RET"
 215 fi
 216 
 217&nbsp;exit $RET</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
>See also <A
HREF="contributed-scripts.html#NIGHTLYBACKUP"
>Example A-34</A
>.</P
><DIV
CLASS="NOTE"
><TABLE
CLASS="NOTE"
WIDTH="90%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="common/note.png"
HSPACE="5"
ALT="Note"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>Using <A
HREF="communications.html#RCPREF"
>rcp</A
>, <A
HREF="communications.html#RSYNCREF"
>rsync</A
>, and similar
	      utilities with security implications in a shell
	      script may not be advisable. Consider, instead, using
	      <B
CLASS="COMMAND"
>ssh</B
>, <A
HREF="communications.html#SCPREF"
>scp</A
>,
	      or an <B
CLASS="COMMAND"
>expect</B
> script.</P
></TD
></TR
></TABLE
></DIV
></DD
><DT
><A
NAME="SSHREF"
></A
><B
CLASS="COMMAND"
>ssh</B
></DT
><DD
><P
><TT
CLASS="REPLACEABLE"
><I
>Secure shell</I
></TT
>, logs onto
	      a remote host and executes commands there. This
	      secure replacement for <B
CLASS="COMMAND"
>telnet</B
>,
	      <B
CLASS="COMMAND"
>rlogin</B
>, <B
CLASS="COMMAND"
>rcp</B
>, and
	      <B
CLASS="COMMAND"
>rsh</B
> uses identity authentication
	      and encryption. See its <A
HREF="external.html#MANREF"
>manpage</A
>
	      for details.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="REMOTE"
></A
><P
><B
>Example 15-43. Using <I
CLASS="FIRSTTERM"
>ssh</I
></B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# remote.bash: Using ssh.
   3&nbsp;
   4&nbsp;# This example by Michael Zick.
   5&nbsp;# Used with permission.
   6&nbsp;
   7&nbsp;
   8&nbsp;#   Presumptions:
   9&nbsp;#   ------------
  10&nbsp;#   fd-2 isn't being captured ( '2&#62;/dev/null' ).
  11&nbsp;#   ssh/sshd presumes stderr ('2') will display to user.
  12&nbsp;#
  13&nbsp;#   sshd is running on your machine.
  14&nbsp;#   For any 'standard' distribution, it probably is,
  15&nbsp;#+  and without any funky ssh-keygen having been done.
  16&nbsp;
  17&nbsp;# Try ssh to your machine from the command line:
  18&nbsp;#
  19&nbsp;# $ ssh $HOSTNAME
  20&nbsp;# Without extra set-up you'll be asked for your password.
  21&nbsp;#   enter password
  22&nbsp;#   when done,  $ exit
  23&nbsp;#
  24&nbsp;# Did that work? If so, you're ready for more fun.
  25&nbsp;
  26&nbsp;# Try ssh to your machine as 'root':
  27&nbsp;#
  28&nbsp;#   $  ssh -l root $HOSTNAME
  29&nbsp;#   When asked for password, enter root's, not yours.
  30&nbsp;#          Last login: Tue Aug 10 20:25:49 2004 from localhost.localdomain
  31&nbsp;#   Enter 'exit' when done.
  32&nbsp;
  33&nbsp;#  The above gives you an interactive shell.
  34&nbsp;#  It is possible for sshd to be set up in a 'single command' mode,
  35&nbsp;#+ but that is beyond the scope of this example.
  36&nbsp;#  The only thing to note is that the following will work in
  37&nbsp;#+ 'single command' mode.
  38&nbsp;
  39&nbsp;
  40&nbsp;# A basic, write stdout (local) command.
  41&nbsp;
  42&nbsp;ls -l
  43&nbsp;
  44&nbsp;# Now the same basic command on a remote machine.
  45&nbsp;# Pass a different 'USERNAME' 'HOSTNAME' if desired:
  46&nbsp;USER=${USERNAME:-$(whoami)}
  47&nbsp;HOST=${HOSTNAME:-$(hostname)}
  48&nbsp;
  49&nbsp;#  Now excute the above command line on the remote host,
  50&nbsp;#+ with all transmissions encrypted.
  51&nbsp;
  52&nbsp;ssh -l ${USER} ${HOST} " ls -l "
  53&nbsp;
  54&nbsp;#  The expected result is a listing of your username's home
  55&nbsp;#+ directory on the remote machine.
  56&nbsp;#  To see any difference, run this script from somewhere
  57&nbsp;#+ other than your home directory.
  58&nbsp;
  59&nbsp;#  In other words, the Bash command is passed as a quoted line
  60&nbsp;#+ to the remote shell, which executes it on the remote machine.
  61&nbsp;#  In this case, sshd does  ' bash -c "ls -l" '   on your behalf.
  62&nbsp;
  63&nbsp;#  For information on topics such as not having to enter a
  64&nbsp;#+ password/passphrase for every command line, see
  65&nbsp;#+    man ssh
  66&nbsp;#+    man ssh-keygen
  67&nbsp;#+    man sshd_config.
  68&nbsp;
  69&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><DIV
CLASS="CAUTION"
><TABLE
CLASS="CAUTION"
WIDTH="90%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="common/caution.png"
HSPACE="5"
ALT="Caution"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>Within a loop, <B
CLASS="COMMAND"
>ssh</B
> may cause
		unexpected behavior. According to a <A
HREF="http://groups-beta.google.com/group/comp.unix.shell/msg/dcb446b5fff7d230"
TARGET="_top"
>		Usenet post</A
> in the comp.unix shell archives,
		<B
CLASS="COMMAND"
>ssh</B
> inherits the loop's
		<TT
CLASS="FILENAME"
>stdin</TT
>. To remedy this, pass
		<B
CLASS="COMMAND"
>ssh</B
> either the <TT
CLASS="OPTION"
>-n</TT
>
		or <TT
CLASS="OPTION"
>-f</TT
> option.</P
><P
>Thanks, Jason Bechtel, for pointing this out.</P
></TD
></TR
></TABLE
></DIV
></DD
><DT
><A
NAME="SCPREF"
></A
><B
CLASS="COMMAND"
>scp</B
></DT
><DD
><P
><TT
CLASS="REPLACEABLE"
><I
>Secure copy</I
></TT
>, similar in
	      function to <B
CLASS="COMMAND"
>rcp</B
>, copies files between
	      two different networked machines, but does so using
	      authentication, and with a security level similar to
	      <B
CLASS="COMMAND"
>ssh</B
>.</P
></DD
></DL
></DIV
><DIV
CLASS="VARIABLELIST"
><P
><B
><A
NAME="COMMLOCAL1"
></A
>Local Network</B
></P
><DL
><DT
><A
NAME="WRITEREF"
></A
><B
CLASS="COMMAND"
>write</B
></DT
><DD
><P
>This is a utility for terminal-to-terminal communication.
	      It allows sending lines from your terminal (console or
	      <I
CLASS="FIRSTTERM"
>xterm</I
>) to that of another user. The
	      <A
HREF="system.html#MESGREF"
>mesg</A
> command may, of course,
	      be used to disable write access to a terminal</P
><P
>Since <B
CLASS="COMMAND"
>write</B
> is interactive, it
	      would not normally find use in a script.</P
></DD
><DT
><A
NAME="NETCONFIGREF"
></A
><B
CLASS="COMMAND"
>netconfig</B
></DT
><DD
><P
>A command-line utility for configuring a network adapter
	      (using <I
CLASS="FIRSTTERM"
>DHCP</I
>). This command is native
	      to Red Hat centric Linux distros.</P
></DD
></DL
></DIV
><DIV
CLASS="VARIABLELIST"
><P
><B
><A
NAME="COMMMAIL1"
></A
>Mail</B
></P
><DL
><DT
><B
CLASS="COMMAND"
>mail</B
></DT
><DD
><P
>Send or read e-mail messages.</P
><P
>This stripped-down command-line mail client
	      works fine as a command embedded in a script.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="SELFMAILER"
></A
><P
><B
>Example 15-44. A script that mails itself</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/sh
   2&nbsp;# self-mailer.sh: Self-mailing script
   3&nbsp;
   4&nbsp;adr=${1:-`whoami`}     # Default to current user, if not specified.
   5&nbsp;#  Typing 'self-mailer.sh [e-mail]'
   6&nbsp;#+ sends this script to that addressee.
   7&nbsp;#  Just 'self-mailer.sh' (no argument) sends the script
   8&nbsp;#+ to the person invoking it, for example, [e-mail].
   9&nbsp;#
  10&nbsp;#  For more on the ${parameter:-default} construct,
  11&nbsp;#+ see the "Parameter Substitution" section
  12&nbsp;#+ of the "Variables Revisited" chapter.
  13&nbsp;
  14&nbsp;# ============================================================================
  15&nbsp;  cat $0 | mail -s "Script \"`basename $0`\" has mailed itself to you." "$adr"
  16&nbsp;# ============================================================================
  17&nbsp;
  18&nbsp;# --------------------------------------------
  19&nbsp;#  Greetings from the self-mailing script.
  20&nbsp;#  A mischievous person has run this script,
  21&nbsp;#+ which has caused it to mail itself to you.
  22&nbsp;#  Apparently, some people have nothing better
  23&nbsp;#+ to do with their time.
  24&nbsp;# --------------------------------------------
  25&nbsp;
  26&nbsp;echo "At `date`, script \"`basename $0`\" mailed to "$adr"."
  27&nbsp;
  28&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
></DD
><DT
><A
NAME="MAILTOREF"
></A
><B
CLASS="COMMAND"
>mailto</B
></DT
><DD
><P
>Similar to the <B
CLASS="COMMAND"
>mail</B
> command,
	      <B
CLASS="COMMAND"
>mailto</B
> sends e-mail messages
	      from the command line or in a script. However,
	      <B
CLASS="COMMAND"
>mailto</B
> also permits sending MIME
	      (multimedia) messages.</P
></DD
><DT
><A
NAME="VACATIONREF"
></A
><B
CLASS="COMMAND"
>vacation</B
></DT
><DD
><P
>This utility automatically replies to e-mails that
	      the intended recipient is on vacation and temporarily
	      unavailable. It runs on a network, in conjunction with
	      <B
CLASS="COMMAND"
>sendmail</B
>, and is not applicable to a
	      dial-up POPmail account.</P
></DD
></DL
></DIV
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
BORDER="0"
CLASS="FOOTNOTES"
WIDTH="100%"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN12186"
HREF="communications.html#AEN12186"
>[1]</A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
><A
NAME="DAEMONREF"
></A
></P
><P
>A <I
CLASS="FIRSTTERM"
>daemon</I
> is a background
		    process not attached to a terminal session. Daemons
		    perform designated services either at specified times
		    or explicitly triggered by certain events.</P
><P
>The word <SPAN
CLASS="QUOTE"
>"daemon"</SPAN
> means ghost in
		    Greek, and there is certainly something mysterious,
		    almost supernatural, about the way UNIX daemons
		    wander about behind the scenes, silently carrying
		    out their appointed tasks.</P
></TD
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