system.html

一本完整的描述Unix Shell 编程的工具书的所有范例

><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
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><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
></TABLE
></DD
><DT
><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
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><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
><B
CLASS="COMMAND"
>stat</B
></DT
><DD
><P
>Gives detailed and verbose <I
CLASS="EMPHASIS"
>stat</I
>istics 
	      on a given file (even a directory or device file) or set
	      of files.</P
><P
>	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><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
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><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
></TABLE
>
	    </P
></DD
><DT
><A
NAME="VMSTATREF"
></A
><B
CLASS="COMMAND"
>vmstat</B
></DT
><DD
><P
>Display virtual memory statistics.</P
><P
>	    <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><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
><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
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><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
></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
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><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
><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"
>$HOSTNAME</A
> internal
	      variable.</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>hostname</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>localhost.localdomain</TT
>
 
 <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>echo $HOSTNAME</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>localhost.localdomain</TT
></PRE
></TD
></TR
></TABLE
><P
>Similar to the <B
CLASS="COMMAND"
>hostname</B
> command are the
	      <B
CLASS="COMMAND"
>domainname</B
>,
	      <B
CLASS="COMMAND"
>dnsdomainname</B
>,
	      <B
CLASS="COMMAND"
>nisdomainname</B
>, and
	      <B
CLASS="COMMAND"
>ypdomainname</B
> commands. Use these to
	      display or set the system DNS or NIS/YP domain name. Various
	      options to <B
CLASS="COMMAND"
>hostname</B
> also perform these
	      functions.</P
></DD
><DT
><A
NAME="HOSTIDREF"
></A
><B
CLASS="COMMAND"
>hostid</B
></DT
><DD
><P
>Echo a 32-bit hexadecimal numerical identifier for the
	      host machine.</P
><P
>	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>hostid</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>7f0100</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
>This command allegedly fetches a <SPAN
CLASS="QUOTE"
>"unique"</SPAN
>
	      serial number for a particular system. Certain
	      product registration procedures use this number
	      to brand a particular user license. Unfortunately,
	      <B
CLASS="COMMAND"
>hostid</B
> only returns the machine
	      network address in hexadecimal, with pairs of bytes
	      transposed.</P
><P
>The network address of a typical non-networked Linux
	      machine, is found in <TT
CLASS="FILENAME"
>/etc/hosts</TT
>.</P
><P
>	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>cat /etc/hosts</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>127.0.0.1               localhost.localdomain localhost</TT
></PRE
></TD
></TR
></TABLE
>
	    </P
><P
>As it happens, transposing the bytes of
	      <TT
CLASS="USERINPUT"
><B
>127.0.0.1</B
></TT
>, we get
	      <TT
CLASS="USERINPUT"
><B
>0.127.1.0</B
></TT
>, which translates in
	      hex to <TT
CLASS="USERINPUT"
><B
>007f0100</B
></TT
>, the exact equivalent
	      of what <B
CLASS="COMMAND"
>hostid</B
> returns, above. There
	      exist only a few million other Linux machines with this
	      identical <I
CLASS="EMPHASIS"
>hostid</I
>.</P
></TD
></TR
></TABLE
></DIV
></DD
><DT
><B
CLASS="COMMAND"
>sar</B
></DT
><DD
><P
>Invoking <B
CLASS="COMMAND"
>sar</B
> (System Activity Reporter)
	      gives a very detailed rundown on system statistics. The
	      Santa Cruz Operation (<SPAN
CLASS="QUOTE"
>"Old"</SPAN
> SCO) released
	      <B
CLASS="COMMAND"
>sar</B
> as Open Source in June, 1999.</P
><P
>This command is not part of the base Linux distribution,
	      but may be obtained as part of the<A
HREF="http://perso.wanadoo.fr/sebastien.godard/"
TARGET="_top"
>	      sysstat utilities</A
> package, written by <A
HREF="mailto:[e-mail]"
TARGET="_top"
>Sebastien
	      Godard</A
>.</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>sar</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>Linux 2.4.9 (brooks.seringas.fr) 	09/26/03

10:30:00          CPU     %user     %nice   %system   %iowait     %idle
10:40:00          all      2.21     10.90     65.48      0.00     21.41
10:50:00          all      3.36      0.00     72.36      0.00     24.28
11:00:00          all      1.12      0.00     80.77      0.00     18.11
Average:          all      2.23      3.63     72.87      0.00     21.27

14:32:30          LINUX RESTART

15:00:00          CPU     %user     %nice   %system   %iowait     %idle
15:10:00          all      8.59      2.40     17.47      0.00     71.54
15:20:00          all      4.07      1.00     11.95      0.00     82.98
15:30:00          all      0.79      2.94      7.56      0.00     88.71
Average:          all      6.33      1.70     14.71      0.00     77.26</TT
>
            </PRE
></TD
></TR
></TABLE
></DD
><DT
><B
CLASS="COMMAND"
>readelf</B
></DT
><DD
><P
>Show information and statistics about a designated
	      <I
CLASS="EMPHASIS"
>elf</I
> binary. This is part of the
	      <I
CLASS="EMPHASIS"
>binutils</I
> package.</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>readelf -h /bin/bash</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>ELF Header:
   Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
   Class:                             ELF32
   Data:                              2's complement, little endian
   Version:                           1 (current)
   OS/ABI:                            UNIX - System V
   ABI Version:                       0
   Type:                              EXEC (Executable file)
   . . .</TT
></PRE
></TD
></TR
></TABLE
></DD
><DT
><B
CLASS="COMMAND"
>size</B
></DT
><DD
><P
>The <B
CLASS="COMMAND"
>size [/path/to/binary]</B
> command
	      gives the segment sizes of a binary executable or archive file.
	      This is mainly of use to programmers.</P
><P
>	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>size /bin/bash</B
></TT
>
 <TT
CLASS="COMPUTEROUTPUT"
>   text    data     bss     dec     hex filename
  495971   22496   17392  535859   82d33 /bin/bash</TT
>
 	      </PRE
></TD
></TR
></TABLE
>
	    </P
></DD
></DL
></DIV
><DIV
CLASS="VARIABLELIST"
><P
><B
><A
NAME="SYSLOG1"
></A
>System Logs</B
></P
><DL
><DT
><B
CLASS="COMMAND"
>logger</B
></DT
><DD
><P
>Appends a user-generated message to the system log
	      (<TT
CLASS="FILENAME"
>/var/log/messages</TT
>). You do not have
	      to be root to invoke <B
CLASS="COMMAND"
>logger</B
>.
	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;logger Experiencing instability in network connection at 23:10, 05/21.
   2&nbsp;# Now, do a 'tail /var/log/messages'.</PRE
></TD
></TR
></TABLE
></P
><P
>By embedding a <B
CLASS="COMMAND"
>logger</B
> command in a script,
	      it is possible to write debugging information to
	      <TT
CLASS="FILENAME"
>/var/log/messages</TT
>.
                 <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;logger -t $0 -i Logging at line "$LINENO".
   2&nbsp;# The "-t" option specifies the tag for the logger entry.
   3&nbsp;# The "-i" option records the process ID.
   4&nbsp;
   5&nbsp;# tail /var/log/message