**sed中&符号的作用详解
sed替换中&符号，经常用来在原文本行中增加字符串。下面通过两个实例讲解&符号的作用**
实例一：
优化开机自动启动服务（不允许用循环语句）。要求开机自动服务只允许network、crond、sshd、rsyslog、iptables、sysstat这几个服务在三运行级别启动，其它服务都关闭。
解答：
第一步筛选出我们想要关闭的服务名称
[root@localhost ~]# chkconfig --list|egrep -v"sshd|rsyslog|network|crond|iptables|sysstat"|awk '{print $1}'
abrt-ccpp
abrtd
acpid
atd
auditd
blk-availability
cpuspeed
haldaemon
ip6tables
irqbalance
kdump
lvm2-monitor
mdmonitor
messagebus
netconsole
netfs
nfs-rdma
ntpd
ntpdate
postfix
psacct
quota_nld
rdisc
rdma
restorecond
rngd
saslauthd
smartd
svnserve
udev-post第二步拼接出”chkconfig 服务名称off”的样式
[root@localhost ~]# chkconfig --list|egrep -v"sshd|rsyslog|network|crond|iptables|sysstat"|awk '{print $1}'|sed's#.*#chkconfig & off#' #=====>这里&符号就是代表前面.*匹配的到字符
chkconfig abrt-ccpp off
chkconfig abrtd off
chkconfig acpid off
chkconfig atd off
chkconfig auditd off
chkconfig blk-availability off
chkconfig cpuspeed off
chkconfig haldaemon off
chkconfig ip6tables off
chkconfig irqbalance off
chkconfig kdump off
chkconfig lvm2-monitor off
chkconfig mdmonitor off
chkconfig messagebus off
chkconfig netconsole off
chkconfig netfs off
chkconfig nfs-rdma off
chkconfig ntpd off
chkconfig ntpdate off
chkconfig postfix off
chkconfig psacct off
chkconfig quota_nld off
chkconfig rdisc off
chkconfig rdma off
chkconfig restorecond off
chkconfig rngd off
chkconfig saslauthd off
chkconfig smartd off
chkconfig svnserve off
chkconfig udev-post off第三步交给bash解释器执行并检查结果
[root@localhost ~]# chkconfig --list|egrep -v"sshd|rsyslog|network|crond|iptables|sysstat"|awk '{print $1}'|sed's#.*#chkconfig & off#'|bash
[root@localhost ~]# chkconfig |grep 3:On
[root@localhost ~]# chkconfig |grep 3:on
crond 0:off 1:off 2:on 3:on 4:on 5:on 6:off
iptables 0:off 1:off 2:on 3:on 4:on 5:on 6:off
network 0:off 1:off 2:on 3:on 4:on 5:on 6:off
rsyslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sshd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sysstat 0:off 1:on 2:on 3:on 4:on 5:on 6:off第二种方法
使用sed替换标志e代表执行(execute)。该标志可以将模式空间中的任何内容当做shell命令执行，并把命令执行的结果返回到模式空间。该标志只有GNU Sed中才可使用。
[root@localhost ~]# chkconfig --list|egrep -v"sshd|rsyslog|network|crond|iptables|sysstat"|awk '{print $1}'|sed's#.*#chkconfig & off#e'
[root@localhost ~]# chkconfig |grep 3:on
crond 0:off 1:off 2:on 3:on 4:on 5:on 6:off
iptables 0:off 1:off 2:on 3:on 4:on 5:on 6:off
network 0:off 1:off 2:on 3:on 4:on 5:on 6:off
rsyslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sshd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sysstat 0:off 1:on 2:on 3:on 4:on 5:on 6:off第三种方法：
[root@localhost ~]#chkconfig |egrep -v "sshd|rsyslog|network|crond|sysstat"|awk '{print$1}'|xargs -i chkconfig {} off实例二：
批量创建10个用户并设置密码（不允许使用循环语句）
第一步跟上面优化服务一样，先创建10个用户名
[root@localhost ~]# echo linux{01..10}|xargs-n1
linux01
linux02
linux03
linux04
linux05
linux06
linux07
linux08
linux09
linux10第二步利用sed的&符号拼接出命令
[root@localhost ~]# echo linux{01..10}|xargs-n1|sed 's#.*#useradd &;echo 123456|passwd --stdin &#'
useradd linux01;echo 123456|passwd --stdinlinux01
useradd linux02;echo 123456|passwd --stdinlinux02
useradd linux03;echo 123456|passwd --stdinlinux03
useradd linux04;echo 123456|passwd --stdinlinux04
useradd linux05;echo 123456|passwd --stdinlinux05
useradd linux06;echo 123456|passwd --stdinlinux06
useradd linux07;echo 123456|passwd --stdinlinux07
useradd linux08;echo 123456|passwd --stdinlinux08
useradd linux09;echo 123456|passwd --stdinlinux09
useradd linux10;echo123456|passwd --stdin linux10第三步利用bash 或sed的e替换符执行拼接出来的命令即可
[root@localhost ~]# echo linux{01..10}|xargs-n1|sed 's#.*#useradd &;echo 123456|passwd --stdin &#'|bash
Changing password for user linux01.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux02.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux03.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux04.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux05.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux06.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux07.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux08.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux09.
passwd: all authentication tokens updatedsuccessfully.
Changing password for user linux10.
passwd: allauthentication tokens updated successfully.第四步检查账户是否被建立
[root@localhost ~]# grep linux /etc/passwd;ll/home/ linux01:x:601:601::/home/linux01:/bin/bash linux02:x:602:602::/home/linux02:/bin/bash linux03:x:603:603::/home/linux03:/bin/bash linux04:x:604:604::/home/linux04:/bin/bash linux05:x:605:605::/home/linux05:/bin/bash linux06:x:606:606::/home/linux06:/bin/bash linux07:x:607:607::/home/linux07:/bin/bash linux08:x:608:608::/home/linux08:/bin/bash linux09:x:609:609::/home/linux09:/bin/bash linux10:x:610:610::/home/linux10:/bin/bash total 40 drwx------ 2 linux01 linux01 4096 May 29 00:57 linux01 drwx------ 2 linux02 linux02 4096 May 29 00:57 linux02 drwx------ 2 linux03 linux03 4096 May 29 00:57 linux03 drwx------ 2 linux04 linux04 4096 May 29 00:57 linux04 drwx------ 2 linux05 linux05 4096 May 29 00:57 linux05 drwx------ 2 linux06 linux06 4096 May 29 00:57 linux06 drwx------ 2 linux07 linux07 4096 May 29 00:57 linux07 drwx------ 2 linux08 linux08 4096 May 29 00:57 linux08 drwx------ 2 linux09 linux09 4096 May 29 00:57 linux09 drwx------ 2 linux10 linux10 4096 May 29 00:57 linux10
sed的&符号总结
1) &符号引用的是前面字符串或正则匹配到的结果 2) &符号常用来拼接字符串 3) &符号常和e替换符执行标志一起使用