退出条件：CONDITION为false
“:” 和true的返回值都为真
[root@centos6mini zuoye]# true
[root@centos6mini zuoye]# echo $?
0
[root@centos6mini zuoye]# :
[root@centos6mini zuoye]# echo $?
0
判断/var/目录下所有文件的类型
[root@centos6mini app]# cat linshi
#!/bin/bash
dc=0
lc=0
cc=0
bc=0
oc=0
zc=0
ls -l /var |grep -v total >/tmp/var_ftype.txt
while read lines
do
ftype=`echo $lines |awk '{print $1}' |cut -c 1`
case $ftype in
d) dname=`echo $lines |awk '{print $9}'`; echo "$dname is a Directory" ; let dc+=1;;
l) lname=`echo $lines |awk '{print $9}'`; echo "$lname is a Links of Soft " ;let lc+=1 ;;
c) cname=`echo $lines |awk '{print $9}'`; echo "$cname is a Character of file" ;let cc+=1;;
b) bname=`echo $lines |awk '{print $9}'`; echo "$bname is a Block file" ; let bc+=1;;
-) zname=`echo $lines |awk '{print $9}'`; echo "$zname is a common file" ; let zc+=1;;
*) echo "Others files"; let oc+=1
esac
done </tmp/var_ftype.txt
echo '-----------------------------'
echo -e "var目录下普通文件数量: $zcnvar目录下子目录数量：$dcnvar目录下链接文件数量：$lcnvar目录下字符类型文件数量: $ccnvar
目录下块设备文件数量：$bcn其他类型文件数量：$oc"
rm -f /tmp/var_ftype.txt
[root@centos6mini app]# ./linshi
cache is a Directory
crash is a Directory
cvs is a Directory
db is a Directory
empty is a Directory
games is a Directory
gdm is a Directory
lib is a Directory
local is a Directory
lock is a Directory
log is a Directory
mail is a Links of Soft
nis is a Directory
opt is a Directory
preserve is a Directory
run is a Directory
spool is a Directory
tmp is a Directory
www is a Directory
yp is a Directory
-----------------------------
var目录下普通文件数量: 0
var目录下子目录数量：19
var目录下链接文件数量：1
var目录下字符类型文件数量: 0
var
目录下块设备文件数量：0
其他类型文件数量：0
编写脚本，求100以内所有正奇数之和
方法一：
[root@centos6mini zuoye]# echo {1..100..2}
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99
[root@centos6mini zuoye]# echo {1..100..2}|tr " " + |bc
2500
方法二：
[root@centos6mini 3.19]# ./1
2500
[root@centos6mini 3.19]# cat 1
#!/bin/bash
u=0
for i in {1..100..2}; do
let u+=i
done
echo $u
方法三：
[root@centos6mini 3.19]# ./1 2500 [root@centos6mini 3.19]# cat 1 #!/bin/bash u=0 i=1 while [ $i -le 100 ] ;do let u+=i let i+=2 done echo $u
编写脚本，提示请输入网络地址，如192.168.0.0，判断输入的网段中主机在线状态，并统计在线和离线主机各多少
方式一：
#!/bin/bash
w=0
a=0
y=0
for (( d=0;d<256;d++ ));do
for (( f=1;f<255;f++ ));do
{
ping -c1 -w1 172.18."$d"."$f" &> /dev/null
a=`echo $?`
if [ $a -eq 0 ] ; then
echo "172.18."$d"."$f" up" >> /app/e.txt
echo "172.18."$d"."$f" up "
fi
if [ $a -ne 0 ] ; then
echo "172.18."$d"."$f" down " >> /app/r.txt
echo "172.18."$d"."$f" down "
fi
}&
done
done
w=`cat /app/e.txt |wc -l`
echo "通的 : $w"
y=`cat /app/r.txt |wc -l`
echo "不通的 : $y"
rm -rf /app/e.txt
rm -rf /app/w.txt
