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<p><FONT class=normalfont><B><font color=blue>在shell程序中判断一个变量是不是由4个数字组成</font></B></FONT><BR><FONT class=smallfont color=#ff9900>2004-04-23 15:18 pm</FONT><BR><FONT class=normalfont>作者：作者<br>来自：Linux知识宝库<br>联系方式：无名<br><br>假设要判断的变量为name，则方法如下：<br>
asd=`echo $name | awk '{<br>
if (substr($1,1,1)>=0 && substr($1,1,1) <=9 &&<br>
substr($1,2,1) >=0 && substr($1,2,1) <=9 &&<br>
substr($1,3,1) >=0 && substr($1,3,1) <=9 &&<br>
substr($1,4,1) >=0 && substr($1,4,1) <=9)<br>
printf("true");<br>
else<br>
printf("false");<br>
<br>
}'`<br>
<br>
if [ asd = "true" ] #是数字<br>
。。。。<br>
elif #不是数字<br>
。。。<br>
<br>
这个办法比较笨，不知其他人有没有更好的方法！<br>
<br>
<br>
<br>
在awk或case语句中对变量使用正则表达式 ^....$ 看其是否匹配就可以了。<br>
<br>
不好意思，应该用正则表达式[0-9][0-9][0-9][0-9]更简单。上面的方法想补救的话，可用<br>
<br>
#！/bin/sh<br>
# test<br>
expr $1 + 10(任意数字) >/dev/null 2>&1<br>
STATUS=$? (测试上条语句是否成功)<br>
if ["$STATUS"!="0"];then<br>
echo "$1 is composed of number"<br>
exit 0 <br>
执行test $name <br>
<br>
# cat zcc<br>
V=$1<br>
if ! echo $V|grep '.....' >/dev/null<br>
then<br>
if echo $V|grep '[0-9][0-9][0-9][0-9]' >/dev/null<br>
then<br>
echo "ok"<br>
else<br>
echo "bad number"<br>
fi<br>
else<br>
echo 'bad number'<br>
fi<br>
# ./zcc 1234<br>
ok.<br>
# ./zcc 123333<br>
bad number<br>
# ./zcc 123<br>
bad number<br>
<br>
试试如何？ <br>
<br>
为何不用case呢?更简单!<br>
case $a in<br>
[0-9][0-9][0-9][0-9]) echo"变量是由4个数字组成";;<br>
*) echo "变量不是由4个数字组成";;<br>
esac<br>
<br>
还是用CASE这种方法比较高。<br>
<br>
借这个帖子提醒大家，模式匹配用了awk,grep,case这些常用的，可别忘了还有expr啊。有时反而更直接。对于本例：<br>
expr $str : '^[0-9][0-9][0-9][0-9]$'<br>
如果值为4就是满足要求的串，否则为0。<br>
<br>
grep,awk,expr,case全用到了。<br>
讨论热烈的一个好贴。<br>
偶用 expr $1 : [0-9]* |grep 4<br>
<br>
valentine ，偷懒可不行啊，对于expr $1 : [0-9]*来说，如果$1="1234a"的话结果也是4。<br>
<br>
michaelds 确实逻辑严密啊。<br>
加个$限制一下好了。<br>
expr $1 : "[0-9]*$" |grep 4<br>
<br>
如果测试变量a<br>
test $a -gt 999 -a $a -lt 10000 2>/dev/nul<br>
再判断$?就OK了<br>
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