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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><HTML><HEAD><TITLE>Complex Commands</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+"><LINKREL="HOME"TITLE="Advanced Bash-Scripting Guide"HREF="index.html"><LINKREL="UP"TITLE="External Filters, Programs and Commands"HREF="external.html"><LINKREL="PREVIOUS"TITLE="External Filters, Programs and Commands"HREF="external.html"><LINKREL="NEXT"TITLE="Time / Date Commands"HREF="timedate.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"><TABLESUMMARY="Header navigation table"WIDTH="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="external.html"ACCESSKEY="P">Prev</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom">Chapter 15. External Filters, Programs and Commands</TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><AHREF="timedate.html"ACCESSKEY="N">Next</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><DIVCLASS="SECT1"><H1CLASS="SECT1"><ANAME="MOREADV"></A>15.2. Complex Commands</H1><DIVCLASS="VARIABLELIST"><P><B><ANAME="CCLISTING1"></A>Commands for more advanced users</B></P><DL><DT><ANAME="FINDREF"></A><BCLASS="COMMAND">find</B></DT><DD><P><ANAME="FINDREF0"></A></P><P>-exec <TTCLASS="REPLACEABLE"><I>COMMAND</I></TT> \;</P><P>Carries out <TTCLASS="REPLACEABLE"><I>COMMAND</I></TT> on each file that <BCLASS="COMMAND">find</B> matches. The command sequence terminates with <SPANCLASS="TOKEN">;</SPAN> (the <SPANCLASS="QUOTE">";"</SPAN> is <AHREF="escapingsection.html#ESCP">escaped</A> to make certain the shell passes it to <BCLASS="COMMAND">find</B> literally, without interpreting it as a special character).</P><P> <TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="90%"><TR><TD><PRECLASS="SCREEN"> <TTCLASS="PROMPT">bash$ </TT><TTCLASS="USERINPUT"><B>find ~/ -name '*.txt'</B></TT> <TTCLASS="COMPUTEROUTPUT">/home/bozo/.kde/share/apps/karm/karmdata.txt /home/bozo/misc/irmeyc.txt /home/bozo/test-scripts/1.txt</TT> </PRE></TD></TR></TABLE> </P><P><ANAME="CURLYBRACKETSREF"></A></P><P>If <TTCLASS="REPLACEABLE"><I>COMMAND</I></TT> contains <SPANCLASS="TOKEN">{}</SPAN>, then <BCLASS="COMMAND">find</B> substitutes the full path name of the selected file for <SPANCLASS="QUOTE">"{}"</SPAN>.</P><P> <TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="90%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 find ~/ -name 'core*' -exec rm {} \; 2 # Removes all core dump files from user's home directory.</PRE></TD></TR></TABLE> </P><P> <TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="90%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 find /home/bozo/projects -mtime 1 2 # Lists all files in /home/bozo/projects directory tree 3 #+ that were modified within the last day. 4 # 5 # mtime = last modification time of the target file 6 # ctime = last status change time (via 'chmod' or otherwise) 7 # atime = last access time 8 9 DIR=/home/bozo/junk_files 10 find "$DIR" -type f -atime +5 -exec rm {} \; 11 # ^^ 12 # Curly brackets are placeholder for the path name output by "find." 13 # 14 # Deletes all files in "/home/bozo/junk_files" 15 #+ that have not been accessed in at least 5 days. 16 # 17 # "-type filetype", where 18 # f = regular file 19 # d = directory 20 # l = symbolic link, etc. 21 # (The 'find' manpage and info page have complete listings.)</PRE></TD></TR></TABLE> </P><P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="90%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 find /etc -exec grep '[0-9][0-9]*[.][0-9][0-9]*[.][0-9][0-9]*[.][0-9][0-9]*' {} \; 2 3 # Finds all IP addresses (xxx.xxx.xxx.xxx) in /etc directory files. 4 # There a few extraneous hits. Can they be filtered out? 5 6 # Possibly by: 7 8 find /etc -type f -exec cat '{}' \; | tr -c '.[:digit:]' '\n' \ 9 | grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$' 10 # 11 # [:digit:] is one of the character classes 12 #+ introduced with the POSIX 1003.2 standard. 13 14 # Thanks, St閜hane Chazelas. </PRE></TD></TR></TABLE></P><DIVCLASS="NOTE"><TABLECLASS="NOTE"WIDTH="90%"BORDER="0"><TR><TDWIDTH="25"ALIGN="CENTER"VALIGN="TOP"><IMGSRC="common/note.png"HSPACE="5"ALT="Note"></TD><TDALIGN="LEFT"VALIGN="TOP"><P>The <TTCLASS="OPTION">-exec</TT> option to <BCLASS="COMMAND">find</B> should not be confused with the <AHREF="internal.html#EXECREF">exec</A> shell builtin.</P></TD></TR></TABLE></DIV><DIVCLASS="EXAMPLE"><HR><ANAME="EX57"></A><P><B>Example 15-3. <ICLASS="FIRSTTERM">Badname</I>, eliminate file names in current directory containing bad characters and <AHREF="special-chars.html#WHITESPACEREF">whitespace</A>.</B></P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="90%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 #!/bin/bash 2 # badname.sh 3 # Delete filenames in current directory containing bad characters. 4 5 for filename in * 6 do 7 badname=`echo "$filename" | sed -n /[\+\{\;\"\\\=\?~\(\)\<\>\&\*\|\$]/p` 8 # badname=`echo "$filename" | sed -n '/[+{;"\=?~()<>&*|$]/p'` also works. 9 # Deletes files containing these nasties: + { ; " \ = ? ~ ( ) < > & * | $ 10 # 11 rm $badname 2>/dev/null 12 # ^^^^^^^^^^^ Error messages deep-sixed. 13 done 14 15 # Now, take care of files containing all manner of whitespace. 16 find . -name "* *" -exec rm -f {} \; 17 # The path name of the file that _find_ finds replaces the "{}". 18 # The '\' ensures that the ';' is interpreted literally, as end of command. 19 20 exit 0 21 22 #--------------------------------------------------------------------- 23 # Commands below this line will not execute because of _exit_ command. 24 25 # An alternative to the above script: 26 find . -name '*[+{;"\\=?~()<>&*|$ ]*' -maxdepth 0 \ 27 -exec rm -f '{}' \; 28 # The "-maxdepth 0" option ensures that _find_ will not search 29 #+ subdirectories below $PWD. 30 31 # (Thanks, S.C.)</PRE></TD></TR></TABLE><HR></DIV><DIVCLASS="EXAMPLE"><HR><ANAME="IDELETE"></A><P><B>Example 15-4. Deleting a file by its <ICLASS="FIRSTTERM">inode</I> number</B></P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="90%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 #!/bin/bash 2 # idelete.sh: Deleting a file by its inode number. 3 4 # This is useful when a filename starts with an illegal character, 5 #+ such as ? or -. 6 7 ARGCOUNT=1 # Filename arg must be passed to script. 8 E_WRONGARGS=70 9 E_FILE_NOT_EXIST=71 10 E_CHANGED_MIND=72 11 12 if [ $# -ne "$ARGCOUNT" ] 13 then 14 echo "Usage: `basename $0` filename" 15 exit $E_WRONGARGS 16 fi 17 18 if [ ! -e "$1" ] 19 then 20 echo "File \""$1"\" does not exist." 21 exit $E_FILE_NOT_EXIST 22 fi 23 24 inum=`ls -i | grep "$1" | awk '{print $1}'` 25 # inum = inode (index node) number of file 26 # ----------------------------------------------------------------------- 27 # Every file has an inode, a record that holds its physical address info. 28 # ----------------------------------------------------------------------- 29 30 echo; echo -n "Are you absolutely sure you want to delete \"$1\" (y/n)? " 31 # The '-v' option to 'rm' also asks this. 32 read answer 33 case "$answer" in 34 [nN]) echo "Changed your mind, huh?" 35 exit $E_CHANGED_MIND 36 ;; 37 *) echo "Deleting file \"$1\".";; 38 esac 39 40 find . -inum $inum -exec rm {} \; 41 # ^^ 42 # Curly brackets are placeholder 43 #+ for text output by "find." 44 echo "File "\"$1"\" deleted!" 45 46 exit 0</PRE></TD></TR></TABLE><HR></DIV><P>The <BCLASS="COMMAND">find</B> command also works without the <TTCLASS="OPTION">-exec</TT> option.</P><P> <TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="90%"><TR><TD><PRECLASS="PROGRAMLISTING"> 1 #!/bin/bash 2 # Find suid root files. 3 # A strange suid file might indicate a security hole, 4 #+ or even a system intrusion. 5 6 directory="/usr/sbin" 7 # Might also try /sbin, /bin, /usr/bin, /usr/local/bin, etc. 8 permissions="+4000" # suid root (dangerous!) 9 10 11 for file in $( find "$directory" -perm "$permissions" ) 12 do 13 ls -ltF --author "$file" 14 done</PRE></TD></TR></TABLE> </P><P>See <AHREF="filearchiv.html#EX48">Example 15-29</A>, <AHREF="special-chars.html#EX58">Example 3-4</A>, and <AHREF="loops.html#FINDSTRING">Example 10-9</A> for scripts using <BCLASS="COMMAND">find</B>. Its <AHREF="external.html#MANREF">manpage</A> provides more detail on this complex and powerful command.</P></DD><DT><ANAME="XARGSREF"></A><BCLASS="COMMAND">xargs</B></DT><DD><P>A filter for feeding arguments to a command, and also a tool for assembling the commands themselves. It breaks a data stream into small enough chunks for filters and commands to process. Consider it as a powerful replacement for <AHREF="commandsub.html#BACKQUOTESREF">backquotes</A>. In situations where <AHREF="commandsub.html#COMMANDSUBREF">command substitution</A> fails with a <SPANCLASS="ERRORNAME">too many arguments</SPAN> error, substituting <BCLASS="COMMAND">xargs</B> often works. <ANAME="AEN9532"HREF="#FTN.AEN9532">[1]</A> Normally, <BCLASS="COMMAND">xargs</B> reads from <TTCLASS="FILENAME">stdin</TT> or from a pipe, but it can also be given the output of a file.</P⌨️ 快捷键说明
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