**sed中&符號的作用詳解
sed替換中&符號，經常用來在原文本行中增加字符串。下面通過兩個實例講解&符號的作用**
實例一：
優化開機自動啓動服務（不允許用循環語句）。要求開機自動服務只允許network、crond、sshd、rsyslog、iptables、sysstat這幾個服務在三運行級別啓動，其它服務都關閉。
解答：
第一步篩選出我們想要關閉的服務名稱
[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 服務名稱off”的樣式
[root@localhost ~]# chkconfig --list|egrep -v"sshd|rsyslog|network|crond|iptables|sysstat"|awk '{print $1}'|sed's#.*#chkconfig & off#' #=====>這裏&符號就是代表前面.*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第三步交給bash解釋器執行並檢查結果
[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第二種方法
使用sed替換標誌e代表執行(execute)。該標誌可以將模式空間中的任何內容當做shell命令執行，並把命令執行的結果返回到模式空間。該標誌只有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第三種方法：
[root@localhost ~]#chkconfig |egrep -v "sshd|rsyslog|network|crond|sysstat"|awk '{print$1}'|xargs -i chkconfig {} off實例二：
批量創建10個用戶並設置密碼（不允許使用循環語句）
第一步跟上面優化服務一樣，先創建10個用戶名
[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&符號拼接出命令
[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替換符執行拼接出來的命令即可
[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.第四步檢查賬戶是否被建立
[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&符號總結
1) &符號引用的是前面字符串或正則匹配到的結果 2) &符號常用來拼接字符串 3) &符號常和e替換符執行標誌一起使用