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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><HTML><HEAD><TITLE>/proc</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.57"><LINKREL="HOME"TITLE="Advanced Bash-Scripting Guide"HREF="index.html"><LINKREL="UP"TITLE="/dev and /proc"HREF="devproc.html"><LINKREL="PREVIOUS"TITLE="/dev and /proc"HREF="devproc.html"><LINKREL="NEXT"TITLE="Of Zeros and Nulls"HREF="zeros.html"><METAHTTP-EQUIV="Content-Style-Type"CONTENT="text/css"><LINKREL="stylesheet"HREF="common/kde-common.css"TYPE="text/css"><METAHTTP-EQUIV="Content-Type"CONTENT="text/html; charset=iso-8859-1"><METAHTTP-EQUIV="Content-Language"CONTENT="en"><LINKREL="stylesheet"HREF="common/kde-localised.css"TYPE="text/css"TITLE="KDE-English"><LINKREL="stylesheet"HREF="common/kde-default.css"TYPE="text/css"TITLE="KDE-Default"></HEAD><BODYCLASS="SECT1"BGCOLOR="#FFFFFF"TEXT="#000000"LINK="#AA0000"VLINK="#AA0055"ALINK="#AA0000"STYLE="font-family: sans-serif;"><DIVCLASS="NAVHEADER"><TABLEWIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">Advanced Bash-Scripting Guide: An in-depth exploration of the art of shell scripting</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><AHREF="devproc.html">Prev</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom">Chapter 27. /dev and /proc</TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><AHREF="zeros.html">Next</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><DIVCLASS="SECT1"><H1CLASS="SECT1"><ANAME="PROCREF1">27.2. <TTCLASS="FILENAME">/proc</TT></A></H1><P>The <TTCLASS="FILENAME">/proc</TT> directory is actually a pseudo-filesystem. The files in <TTCLASS="FILENAME">/proc</TT> mirror currently running system and kernel <ICLASS="EMPHASIS">processes</I> and contain information and statistics about them.</P><P> <TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><PRECLASS="SCREEN"> <TTCLASS="PROMPT">bash$ </TT><TTCLASS="USERINPUT"><B>cat /proc/devices</B></TT> <TTCLASS="COMPUTEROUTPUT">Character devices: 1 mem 2 pty 3 ttyp 4 ttyS 5 cua 7 vcs 10 misc 14 sound 29 fb 36 netlink 128 ptm 136 pts 162 raw 254 pcmcia Block devices: 1 ramdisk 2 fd 3 ide0 9 md</TT> <TTCLASS="PROMPT">bash$ </TT><TTCLASS="USERINPUT"><B>cat /proc/interrupts</B></TT> <TTCLASS="COMPUTEROUTPUT"> CPU0 0: 84505 XT-PIC timer 1: 3375 XT-PIC keyboard 2: 0 XT-PIC cascade 5: 1 XT-PIC soundblaster 8: 1 XT-PIC rtc 12: 4231 XT-PIC PS/2 Mouse 14: 109373 XT-PIC ide0 NMI: 0 ERR: 0</TT> <TTCLASS="PROMPT">bash$ </TT><TTCLASS="USERINPUT"><B>cat /proc/partitions</B></TT> <TTCLASS="COMPUTEROUTPUT">major minor #blocks name rio rmerge rsect ruse wio wmerge wsect wuse running use aveq 3 0 3007872 hda 4472 22260 114520 94240 3551 18703 50384 549710 0 111550 644030 3 1 52416 hda1 27 395 844 960 4 2 14 180 0 800 1140 3 2 1 hda2 0 0 0 0 0 0 0 0 0 0 0 3 4 165280 hda4 10 0 20 210 0 0 0 0 0 210 210 ...</TT> <TTCLASS="PROMPT">bash$ </TT><TTCLASS="USERINPUT"><B>cat /proc/loadavg</B></TT> <TTCLASS="COMPUTEROUTPUT">0.13 0.42 0.27 2/44 1119</TT> <TTCLASS="PROMPT">bash$ </TT><TTCLASS="USERINPUT"><B>cat /proc/apm</B></TT> <TTCLASS="COMPUTEROUTPUT">1.16 1.2 0x03 0x01 0xff 0x80 -1% -1 ?</TT> </PRE></TD></TR></TABLE> </P><P>Shell scripts may extract data from certain of the files in <TTCLASS="FILENAME">/proc</TT>. <ANAME="AEN14673"HREF="#FTN.AEN14673">[1]</A></P><P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 FS=iso # ISO filesystem support in kernel? 2 3 grep $FS /proc/filesystems # iso9660</PRE></TD></TR></TABLE></P><P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 kernel_version=$( awk '{ print $3 }' /proc/version )</PRE></TD></TR></TABLE></P><P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 CPU=$( awk '/model name/ {print $4}' < /proc/cpuinfo ) 2 3 if [ $CPU = Pentium ] 4 then 5 run_some_commands 6 ... 7 else 8 run_different_commands 9 ... 10 fi</PRE></TD></TR></TABLE></P><P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 devfile="/proc/bus/usb/devices" 2 USB1="Spd=12" 3 USB2="Spd=480" 4 5 6 bus_speed=$(grep Spd $devfile | awk '{print $9}') 7 8 if [ "$bus_speed" = "$USB1" ] 9 then 10 echo "USB 1.1 port found." 11 # Do something appropriate for USB 1.1. 12 fi</PRE></TD></TR></TABLE></P><P>The <TTCLASS="FILENAME">/proc</TT> directory contains subdirectories with unusual numerical names. Every one of these names maps to the <AHREF="variables2.html#PPIDREF">process ID</A> of a currently running process. Within each of these subdirectories, there are a number of files that hold useful information about the corresponding process. The <TTCLASS="FILENAME">stat</TT> and <TTCLASS="FILENAME">status</TT> files keep running statistics on the process, the <TTCLASS="FILENAME">cmdline</TT> file holds the command-line arguments the process was invoked with, and the <TTCLASS="FILENAME">exe</TT> file is a symbolic link to the complete path name of the invoking process. There are a few more such files, but these seem to be the most interesting from a scripting standpoint.</P><DIVCLASS="EXAMPLE"><HR><ANAME="PIDID"></A><P><B>Example 27-2. Finding the process associated with a PID</B></P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 #!/bin/bash 2 # pid-identifier.sh: Gives complete path name to process associated with pid. 3 4 ARGNO=1 # Number of arguments the script expects. 5 E_WRONGARGS=65 6 E_BADPID=66 7 E_NOSUCHPROCESS=67 8 E_NOPERMISSION=68 9 PROCFILE=exe 10 11 if [ $# -ne $ARGNO ] 12 then 13 echo "Usage: `basename $0` PID-number" >&2 # Error message >stderr. 14 exit $E_WRONGARGS 15 fi 16 17 pidno=$( ps ax | grep $1 | awk '{ print $1 }' | grep $1 ) 18 # Checks for pid in "ps" listing, field #1. 19 # Then makes sure it is the actual process, not the process invoked by this script. 20 # The last "grep $1" filters out this possibility. 21 # 22 # pidno=$( ps ax | awk '{ print $1 }' | grep $1 ) 23 # also works, as Teemu Huovila, points out. 24 25 if [ -z "$pidno" ] # If, after all the filtering, the result is a zero-length string, 26 then # no running process corresponds to the pid given. 27 echo "No such process running." 28 exit $E_NOSUCHPROCESS 29 fi 30 31 # Alternatively: 32 # if ! ps $1 > /dev/null 2>&1 33 # then # no running process corresponds to the pid given. 34 # echo "No such process running." 35 # exit $E_NOSUCHPROCESS 36 # fi 37 38 # To simplify the entire process, use "pidof". 39 40 41 if [ ! -r "/proc/$1/$PROCFILE" ] # Check for read permission. 42 then 43 echo "Process $1 running, but..." 44 echo "Can't get read permission on /proc/$1/$PROCFILE." 45 exit $E_NOPERMISSION # Ordinary user can't access some files in /proc. 46 fi 47 48 # The last two tests may be replaced by: 49 # if ! kill -0 $1 > /dev/null 2>&1 # '0' is not a signal, but 50 # this will test whether it is possible 51 # to send a signal to the process. 52 # then echo "PID doesn't exist or you're not its owner" >&2 53 # exit $E_BADPID 54 # fi 55 56 57 58 exe_file=$( ls -l /proc/$1 | grep "exe" | awk '{ print $11 }' ) 59 # Or exe_file=$( ls -l /proc/$1/exe | awk '{print $11}' ) 60 # 61 # /proc/pid-number/exe is a symbolic link 62 # to the complete path name of the invoking process. 63 64 if [ -e "$exe_file" ] # If /proc/pid-number/exe exists... 65 then # the corresponding process exists. 66 echo "Process #$1 invoked by $exe_file." 67 else 68 echo "No such process running." 69 fi 70 71 72 # This elaborate script can *almost* be replaced by 73 # ps ax | grep $1 | awk '{ print $5 }' 74 # However, this will not work... 75 # because the fifth field of 'ps' is argv[0] of the process, 76 # not the executable file path. 77 # 78 # However, either of the following would work. 79 # find /proc/$1/exe -printf '%l\n' 80 # lsof -aFn -p $1 -d txt | sed -ne 's/^n//p' 81 82 # Additional commentary by Stephane Chazelas. 83 84 exit 0</PRE></TD></TR></TABLE><HR></DIV><DIVCLASS="EXAMPLE"><HR><ANAME="CONSTAT"></A><P><B>Example 27-3. On-line connect status</B></P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 #!/bin/bash 2 3 PROCNAME=pppd # ppp daemon 4 PROCFILENAME=status # Where to look. 5 NOTCONNECTED=65 6 INTERVAL=2 # Update every 2 seconds. 7 8 pidno=$( ps ax | grep -v "ps ax" | grep -v grep | grep $PROCNAME | awk '{ print $1 }' ) 9 # Finding the process number of 'pppd', the 'ppp daemon'. 10 # Have to filter out the process lines generated by the search itself. 11 # 12 # However, as Oleg Philon points out, 13 #+ this could have been considerably simplified by using "pidof". 14 # pidno=$( pidof $PROCNAME ) 15 # 16 # Moral of the story: 17 #+ When a command sequence gets too complex, look for a shortcut. 18 19 20 if [ -z "$pidno" ] # If no pid, then process is not running. 21 then 22 echo "Not connected." 23 exit $NOTCONNECTED 24 else 25 echo "Connected."; echo 26 fi 27 28 while [ true ] # Endless loop, script can be improved here. 29 do 30 31 if [ ! -e "/proc/$pidno/$PROCFILENAME" ] 32 # While process running, then "status" file exists. 33 then 34 echo "Disconnected." 35 exit $NOTCONNECTED 36 fi 37 38 netstat -s | grep "packets received" # Get some connect statistics. 39 netstat -s | grep "packets delivered" 40 41 42 sleep $INTERVAL 43 echo; echo 44 45 done 46 47 exit 0 48 49 # As it stands, this script must be terminated with a Control-C. 50 51 # Exercises: 52 # --------- 53 # Improve the script so it exits on a "q" keystroke. 54 # Make the script more user-friendly in other ways.</PRE></TD></TR></TABLE><HR></DIV><DIVCLASS="WARNING"><TABLECLASS="WARNING"WIDTH="100%"BORDER="0"><TR><TDWIDTH="25"ALIGN="CENTER"VALIGN="TOP"><IMGSRC="common/warning.png"HSPACE="5"ALT="Warning"></TD><TDALIGN="LEFT"VALIGN="TOP"><P>In general, it is dangerous to <ICLASS="EMPHASIS">write</I> to the files in <TTCLASS="FILENAME">/proc</TT>, as this can corrupt the filesystem or crash the machine.</P></TD></TR></TABLE></DIV></DIV><H3CLASS="FOOTNOTES">Notes</H3><TABLEBORDER="0"CLASS="FOOTNOTES"WIDTH="100%"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="5%"><ANAME="FTN.AEN14673"HREF="procref1.html#AEN14673">[1]</A></TD><TDALIGN="LEFT"VALIGN="TOP"WIDTH="95%"><P>Certain system commands, such as <AHREF="system.html#PROCINFOREF">procinfo</A>, <AHREF="system.html#FREEREF">free</A>, <AHREF="system.html#VMSTATREF">vmstat</A>, <AHREF="system.html#LSDEVREF">lsdev</A>, and <AHREF="system.html#UPTIMEREF">uptime</A> do this as well.</P></TD></TR></TABLE><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLEWIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><AHREF="devproc.html">Prev</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="index.html">Home</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><AHREF="zeros.html">Next</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">/dev and /proc</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="devproc.html">Up</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">Of Zeros and Nulls</TD></TR></TABLE></DIV></BODY></HTML>⌨️ 快捷键说明
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