system.html

Shall高级编程

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CLASS="PROGRAMLISTING"
>   1&nbsp;#! /bin/sh
   2&nbsp;## Duplicate DaveG's ident-scan thingie using netcat. Oooh, he'll be p*ssed.
   3&nbsp;## Args: target port [port port port ...]
   4&nbsp;## Hose stdout _and_ stderr together.
   5&nbsp;##
   6&nbsp;##  Advantages: runs slower than ident-scan, giving remote inetd less cause
   7&nbsp;##+ for alarm, and only hits the few known daemon ports you specify.
   8&nbsp;##  Disadvantages: requires numeric-only port args, the output sleazitude,
   9&nbsp;##+ and won't work for r-services when coming from high source ports.
  10&nbsp;# Script author: Hobbit &#60;[e-mail]&#62;
  11&nbsp;# Used in ABS Guide with permission.
  12&nbsp;
  13&nbsp;# ---------------------------------------------------
  14&nbsp;E_BADARGS=65       # Need at least two args.
  15&nbsp;TWO_WINKS=2        # How long to sleep.
  16&nbsp;THREE_WINKS=3
  17&nbsp;IDPORT=113         # Authentication "tap ident" port.
  18&nbsp;RAND1=999
  19&nbsp;RAND2=31337
  20&nbsp;TIMEOUT0=9
  21&nbsp;TIMEOUT1=8
  22&nbsp;TIMEOUT2=4
  23&nbsp;# ---------------------------------------------------
  24&nbsp;
  25&nbsp;case "${2}" in
  26&nbsp;  "" ) echo "Need HOST and at least one PORT." ; exit $E_BADARGS ;;
  27&nbsp;esac
  28&nbsp;
  29&nbsp;# Ping 'em once and see if they *are* running identd.
  30&nbsp;nc -z -w $TIMEOUT0 "$1" $IDPORT || \
  31&nbsp;{ echo "Oops, $1 isn't running identd." ; exit 0 ; }
  32&nbsp;#  -z scans for listening daemons.
  33&nbsp;#     -w $TIMEOUT = How long to try to connect.
  34&nbsp;
  35&nbsp;# Generate a randomish base port.
  36&nbsp;RP=`expr $$ % $RAND1 + $RAND2`
  37&nbsp;
  38&nbsp;TRG="$1"
  39&nbsp;shift
  40&nbsp;
  41&nbsp;while test "$1" ; do
  42&nbsp;  nc -v -w $TIMEOUT1 -p ${RP} "$TRG" ${1} &#60; /dev/null &#62; /dev/null &#38;
  43&nbsp;  PROC=$!
  44&nbsp;  sleep $THREE_WINKS
  45&nbsp;  echo "${1},${RP}" | nc -w $TIMEOUT2 -r "$TRG" $IDPORT 2&#62;&#38;1
  46&nbsp;  sleep $TWO_WINKS
  47&nbsp;
  48&nbsp;# Does this look like a lamer script or what . . . ?
  49&nbsp;# ABS Guide author comments: "Ain't really all that bad . . .
  50&nbsp;#+                            kinda clever, actually."
  51&nbsp;
  52&nbsp;  kill -HUP $PROC
  53&nbsp;  RP=`expr ${RP} + 1`
  54&nbsp;  shift
  55&nbsp;done
  56&nbsp;
  57&nbsp;exit $?
  58&nbsp;
  59&nbsp;#  Notes:
  60&nbsp;#  -----
  61&nbsp;
  62&nbsp;#  Try commenting out line 30 and running this script
  63&nbsp;#+ with "localhost.localdomain 25" as arguments.
  64&nbsp;
  65&nbsp;#  For more of Hobbit's 'nc' example scripts,
  66&nbsp;#+ look in the documentation:
  67&nbsp;#+ the /usr/share/doc/nc-X.XX/scripts directory.</PRE
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><HR></DIV
><P
>	      And, of course, there's Dr. Andrew Tridgell's notorious
	      one-line script in the BitKeeper Affair:
	        <TABLE
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><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;echo clone | nc thunk.org 5000 &#62; e2fsprogs.dat</PRE
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>
	    </P
></DD
><DT
><A
NAME="FREEREF"
></A
><B
CLASS="COMMAND"
>free</B
></DT
><DD
><P
>Shows memory and cache usage in tabular form. The
	      output of this command lends itself to parsing, using
	      <A
HREF="textproc.html#GREPREF"
>grep</A
>, <A
HREF="awk.html#AWKREF"
>awk</A
> or <B
CLASS="COMMAND"
>Perl</B
>. The
	      <B
CLASS="COMMAND"
>procinfo</B
> command shows all the
	      information that <B
CLASS="COMMAND"
>free</B
> does, and much
	      more.</P
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><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><B
CLASS="COMMAND"
>free</B
>
 <TT
CLASS="COMPUTEROUTPUT"
>                total       used       free     shared    buffers     cached
   Mem:         30504      28624       1880      15820       1608       16376
   -/+ buffers/cache:      10640      19864
   Swap:        68540       3128      65412</TT
></PRE
></TD
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><P
>To show unused RAM memory:</P
><TABLE
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><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><B
CLASS="COMMAND"
>free | grep Mem | awk '{ print $4 }'</B
>
 <TT
CLASS="COMPUTEROUTPUT"
>1880</TT
></PRE
></TD
></TR
></TABLE
></DD
><DT
><A
NAME="PROCINFOREF"
></A
><B
CLASS="COMMAND"
>procinfo</B
></DT
><DD
><P
>Extract and list information and statistics from the
	      <A
HREF="devproc.html#DEVPROCREF"
><TT
CLASS="FILENAME"
>/proc</TT
>
	      pseudo-filesystem</A
>. This gives a very extensive and
	      detailed listing.</P
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><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>procinfo | grep Bootup</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>Bootup: Wed Mar 21 15:15:50 2001    Load average: 0.04 0.21 0.34 3/47 6829</TT
></PRE
></TD
></TR
></TABLE
></DD
><DT
><A
NAME="LSDEVREF"
></A
><B
CLASS="COMMAND"
>lsdev</B
></DT
><DD
><P
>List devices, that is, show installed hardware.</P
><P
>	      <TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>lsdev</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>Device            DMA   IRQ  I/O Ports
 ------------------------------------------------
 cascade             4     2 
 dma                          0080-008f
 dma1                         0000-001f
 dma2                         00c0-00df
 fpu                          00f0-00ff
 ide0                     14  01f0-01f7 03f6-03f6
 ...</TT
>
 	      </PRE
></TD
></TR
></TABLE
>
	      </P
></DD
><DT
><A
NAME="DUREF"
></A
><B
CLASS="COMMAND"
>du</B
></DT
><DD
><P
>Show (disk) file usage, recursively. Defaults to current
	      working directory, unless otherwise specified.</P
><TABLE
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><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><B
CLASS="COMMAND"
>du -ach</B
>
 <TT
CLASS="COMPUTEROUTPUT"
>1.0k    ./wi.sh
 1.0k    ./tst.sh
 1.0k    ./random.file
 6.0k    .
 6.0k    total</TT
></PRE
></TD
></TR
></TABLE
></DD
><DT
><A
NAME="DFREF"
></A
><B
CLASS="COMMAND"
>df</B
></DT
><DD
><P
>Shows filesystem usage in tabular form.</P
><TABLE
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><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><B
CLASS="COMMAND"
>df</B
>
 <TT
CLASS="COMPUTEROUTPUT"
>Filesystem           1k-blocks      Used Available Use% Mounted on
 /dev/hda5               273262     92607    166547  36% /
 /dev/hda8               222525    123951     87085  59% /home
 /dev/hda7              1408796   1075744    261488  80% /usr</TT
></PRE
></TD
></TR
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></DD
><DT
><A
NAME="DMESGREF"
></A
><B
CLASS="COMMAND"
>dmesg</B
></DT
><DD
><P
>Lists all system bootup messages to
	      <TT
CLASS="FILENAME"
>stdout</TT
>. Handy for debugging and
	      ascertaining which device drivers were installed
	      and which system interrupts in use. The output
	      of <B
CLASS="COMMAND"
>dmesg</B
> may, of course, be
	      parsed with <A
HREF="textproc.html#GREPREF"
>grep</A
>,
	      <A
HREF="sedawk.html#SEDREF"
>sed</A
>, or <A
HREF="awk.html#AWKREF"
>awk</A
> from within a script.</P
><P
>	      <TABLE
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><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>dmesg | grep hda</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>Kernel command line: ro root=/dev/hda2
 hda: IBM-DLGA-23080, ATA DISK drive
 hda: 6015744 sectors (3080 MB) w/96KiB Cache, CHS=746/128/63
 hda: hda1 hda2 hda3 &#60; hda5 hda6 hda7 &#62; hda4</TT
>
 	      </PRE
></TD
></TR
></TABLE
>
	    </P
></DD
><DT
><A
NAME="STATREF"
></A
><B
CLASS="COMMAND"
>stat</B
></DT
><DD
><P
>Gives detailed and verbose <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>stat</I
></SPAN
>istics 
	      on a given file (even a directory or device file) or set
	      of files.</P
><P
>	      <TABLE
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><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>stat test.cru</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>  File: "test.cru"
   Size: 49970        Allocated Blocks: 100          Filetype: Regular File
   Mode: (0664/-rw-rw-r--)         Uid: (  501/ bozo)  Gid: (  501/ bozo)
 Device:  3,8   Inode: 18185     Links: 1    
 Access: Sat Jun  2 16:40:24 2001
 Modify: Sat Jun  2 16:40:24 2001
 Change: Sat Jun  2 16:40:24 2001</TT
>
 	      </PRE
></TD
></TR
></TABLE
>
	    </P
><P
>If the target file does not exist, <B
CLASS="COMMAND"
>stat</B
>
	      returns an error message.</P
><P
>	      <TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>stat nonexistent-file</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>nonexistent-file: No such file or directory</TT
>
 	      </PRE
></TD
></TR
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>
	    </P
><P
>In a script, you can use <B
CLASS="COMMAND"
>stat</B
> to extract
	      information about files (and filesystems) and set variables
	      accordingly.</P
><P
>	      <TABLE
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><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# fileinfo2.sh
   3&nbsp;
   4&nbsp;# Per suggestion of Jo雔 Bourquard and . . .
   5&nbsp;# http://www.linuxquestions.org/questions/showthread.php?t=410766
   6&nbsp;
   7&nbsp;
   8&nbsp;FILENAME=testfile.txt
   9&nbsp;file_name=$(stat -c%n "$FILENAME")   # Same as "$FILENAME" of course.
  10&nbsp;file_owner=$(stat -c%U "$FILENAME")
  11&nbsp;file_size=$(stat -c%s "$FILENAME")
  12&nbsp;#  Certainly easier than using "ls -l $FILENAME"
  13&nbsp;#+ and then parsing with sed.
  14&nbsp;file_inode=$(stat -c%i "$FILENAME")
  15&nbsp;file_type=$(stat -c%F "$FILENAME")
  16&nbsp;file_access_rights=$(stat -c%A "$FILENAME")
  17&nbsp;
  18&nbsp;echo "File name:          $file_name"
  19&nbsp;echo "File owner:         $file_owner"
  20&nbsp;echo "File size:          $file_size"
  21&nbsp;echo "File inode:         $file_inode"
  22&nbsp;echo "File type:          $file_type"
  23&nbsp;echo "File access rights: $file_access_rights"
  24&nbsp;
  25&nbsp;exit 0
  26&nbsp;
  27&nbsp;sh fileinfo2.sh
  28&nbsp;
  29&nbsp;File name:          testfile.txt
  30&nbsp;File owner:         bozo
  31&nbsp;File size:          418
  32&nbsp;File inode:         1730378
  33&nbsp;File type:          regular file
  34&nbsp;File access rights: -rw-rw-r--</PRE
></TD
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>
	    </P
></DD
><DT
><A
NAME="VMSTATREF"
></A
><B
CLASS="COMMAND"
>vmstat</B
></DT
><DD
><P
>Display virtual memory statistics.</P
><P
>	    <TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>vmstat</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>   procs                      memory    swap          io system         cpu
 r  b  w   swpd   free   buff  cache  si  so    bi    bo   in    cs  us  sy id
 0  0  0      0  11040   2636  38952   0   0    33     7  271    88   8   3 89</TT
>
 	    </PRE
></TD
></TR
></TABLE
>
	    </P
></DD
><DT
><A
NAME="NETSTATREF"
></A
><B
CLASS="COMMAND"
>netstat</B
></DT
><DD
><P
>Show current network statistics and information, 
	      such as routing tables and active connections. This utility
	      accesses information in <TT
CLASS="FILENAME"
>/proc/net</TT
>
	      (<A
HREF="devproc.html"
>Chapter 27</A
>). See <A
HREF="procref1.html#CONSTAT"
>Example 27-3</A
>.</P
><P
><B
CLASS="COMMAND"
>netstat -r</B
> is equivalent to <A
HREF="system.html#ROUTEREF"
>route</A
>.</P
><TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>netstat</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>Active Internet connections (w/o servers)
 Proto Recv-Q Send-Q Local Address           Foreign Address         State      
 Active UNIX domain sockets (w/o servers)
 Proto RefCnt Flags       Type       State         I-Node Path
 unix  11     [ ]         DGRAM                    906    /dev/log
 unix  3      [ ]         STREAM     CONNECTED     4514   /tmp/.X11-unix/X0
 unix  3      [ ]         STREAM     CONNECTED     4513
 . . .</TT
></PRE
></TD
></TR
></TABLE
><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
>A <B
CLASS="COMMAND"
>netstat -lptu</B
> shows <A
HREF="devproc.html#SOCKETREF"
>sockets</A
> that are listening
	    to ports, and the associated processes. This can be useful
	    for determining whether a computer has been hacked or
	    compromised.</P
></TD
></TR
></TABLE
></DIV
></DD
><DT
><A
NAME="UPTIMEREF"
></A
><B
CLASS="COMMAND"
>uptime</B
></DT
><DD
><P
>Shows how long the system has been running, along with
	      associated statistics.</P
><P
>	    <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
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><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>uptime</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>10:28pm  up  1:57,  3 users,  load average: 0.17, 0.34, 0.27</TT
></PRE
></TD
></TR
></TABLE
>
	    </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
>A <I
CLASS="FIRSTTERM"
>load average</I
> of 1 or less
	      indicates that the system handles processes immediately. A load
	      average greater than 1 means that processes are being queued. When
	      the load average gets above 3, then system performance is
	      significantly degraded.</P
></TD
></TR
></TABLE
></DIV
></DD
><DT
><A
NAME="HNAMEREF"
></A
><B
CLASS="COMMAND"
>hostname</B
></DT
><DD
><P
>Lists the system's host name. This command sets the host
	      name in an <TT
CLASS="FILENAME"
>/etc/rc.d</TT
>
	      setup script (<TT
CLASS="FILENAME"
>/etc/rc.d/rc.sysinit</TT
>
	      or similar).  It is equivalent to <B
CLASS="COMMAND"
>uname
	      -n</B
>,  and a counterpart to the <A
HREF="variables2.html#HOSTNAMEREF"
>$HOSTNAME</A
> internal
	      variable.</P
><TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>hostname</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>localhost.localdomain</TT
>
 
 <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>echo $HOSTNAME</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>localhost.localdomain</TT
></PRE
></TD
></TR
></TABLE
><P
>Similar to the <B
CLASS="COMMAND"
>hostname</B
> command are the