＃截取字符串-1
aa="`ifconfig eth0 | grep 'inet addr' | awk '{print $2}'`"
echo $aa | grep -o '[0-9]+.[0-9]+.[0-9]+.[0-9]+'

[@more@]

＃截取字符串-1
aa="`ifconfig eth0 | grep 'inet addr' | awk '{print $2}'`"
echo $aa | grep -o '[0-9]+.[0-9]+.[0-9]+.[0-9]+'

＃截取字符串-2
ifconfig eth0 | grep 'inet addr' | awk '{print $2}' | cut -c6-20

＃截取字符串-3
aa="`ifconfig eth0 | grep 'inet addr' | awk '{print $2}'`"
echo ${aa:6:20}

#截取字符串-4

那就有两种情况了，一种要留分界符的，一种不要的，这样可以吧，分两步：
//分界符
$D = ",";
//要抽取的串
$S = "12";

//在中间时要留分界符
$str = ereg_replace("($D$S$D)", "$D", $str);

//单独或在结尾或在开头时不要留分界符，直接删除
$str = ereg_replace("(^$S$D|$D$S$|^$S$)", "", $str);

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linux下的shell编程之--截取字符串

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