正则表达式小练习

题目要求：

一.找出"netstat -tan”命令的结果中，以‘LISTEN’后跟0或多个空白字符结尾的行

二.在/etc/fstab文件中不以#开头的行的行首增加#号

三.删除/etc/fstab文件中所有以#开头的#字符

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题目要求：

1.找出"netstat -tan”命令的结果中，以‘LISTEN’后跟0或多个空白字符结尾的行
​2.在/etc/fstab文件中不以#开头的行的行首增加#号
​3.删除/etc/fstab文件中所有以#开头的#字符

一.找出"netstat -tan”命令的结果中，以‘LISTEN’后跟0或多个空白字符结尾的行

[root@localhost aaa]# netstat -tan | grep "LISTEN[[:space:]]*\>"
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN
tcp        0      0 192.168.122.1:53        0.0.0.0:*               LISTEN
tcp        0      0 192.168.2.226:53        0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:53            0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:953           0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:6010          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:6011          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:6012          0.0.0.0:*               LISTEN
tcp6       0      0 :::111                  :::*                    LISTEN
tcp6       0      0 :::80                   :::*                    LISTEN
tcp6       0      0 :::53                   :::*                    LISTEN
tcp6       0      0 :::22                   :::*                    LISTEN
tcp6       0      0 ::1:631                 :::*                    LISTEN
tcp6       0      0 ::1:953                 :::*                    LISTEN
tcp6       0      0 ::1:6010                :::*                    LISTEN
tcp6       0      0 ::1:6011                :::*                    LISTEN
tcp6       0      0 ::1:6012                :::*                    LISTEN

二.在/etc/fstab文件中不以#开头的行的行首增加#号

[root@localhost aaa]# cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Thu Apr  6 09:20:08 2023
#
# Accessible filesystems, by reference, are maintained under '/dev/disk/'.
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info.
#
# After editing this file, run 'systemctl daemon-reload' to update systemd
# units generated from this file.
#
/dev/mapper/rhel-root   /                       xfs     defaults        0 0
UUID=f7e1da57-79b9-4254-be42-45fbb0bc7c05 /boot                   xfs     defaults        0 0
/dev/mapper/rhel-swap   none                    swap    defaults        0 0
/dev/sr0 /cdrom iso9660 defaults,_netdev 0 0
[root@localhost aaa]# sed "s/^[^#]/#/" /etc/fstab

#
# /etc/fstab
# Created by anaconda on Thu Apr  6 09:20:08 2023
#
# Accessible filesystems, by reference, are maintained under '/dev/disk/'.
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info.
#
# After editing this file, run 'systemctl daemon-reload' to update systemd
# units generated from this file.
#
#dev/mapper/rhel-root   /                       xfs     defaults        0 0
#UID=f7e1da57-79b9-4254-be42-45fbb0bc7c05 /boot                   xfs     defaults        0 0
#dev/mapper/rhel-swap   none                    swap    defaults        0 0
#dev/sr0 /cdrom iso9660 defaults,_netdev 0 0

三.删除/etc/fstab文件中所有以#开头的#字符

[root@localhost aaa]# sed "s/#//" /etc/fstab


 /etc/fstab
 Created by anaconda on Thu Apr  6 09:20:08 2023

 Accessible filesystems, by reference, are maintained under '/dev/disk/'.
 See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info.

 After editing this file, run 'systemctl daemon-reload' to update systemd
 units generated from this file.

/dev/mapper/rhel-root   /                       xfs     defaults        0 0
UUID=f7e1da57-79b9-4254-be42-45fbb0bc7c05 /boot                   xfs     defaults        0 0
/dev/mapper/rhel-swap   none                    swap    defaults        0 0
/dev/sr0 /cdrom iso9660 defaults,_netdev 0 0