文本处理工具sed练习

1、利用sed 取出ifconfig命令中本机的IPv4地址

[root@centos8 ~]# ifconfig ens33
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.0.101  netmask 255.255.255.0  broadcast 10.0.0.255
        inet6 fe80::20c:29ff:fec0:d588  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:c0:d5:88  txqueuelen 1000  (Ethernet)
        RX packets 3558  bytes 319499 (312.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8553  bytes 8285509 (7.9 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
[root@centos8 ~]# ifconfig ens33 | sed -nr "2s/[^0-9]+([0-9.]+).*/\1/p"
10.0.0.101

2、删除/etc/fstab文件中所有以#开头，后面至少跟一个空白字符的行的行首的#和空白字符

[root@centos8 ~]# cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Mon Nov  8 15:06:40 2021
#
# 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.
#
UUID=7e52ecef-fcd5-4767-a018-b78c85d5be0e /                       xfs     defaults        0 0
UUID=3c1d9414-9115-43ba-84fb-401472776367 /boot                   ext4    defaults        1 2
UUID=e97181be-696b-47c9-8c42-5c539598cea4 /data                   xfs     defaults        0 0
UUID=2d32ba3e-4ff7-4df6-bd34-748c877c1bda none                    swap    defaults        0 0
[root@centos8 ~]# sed -i.bak '/^# */d;/^$/d' /etc/fstab
[root@centos8 ~]# cat /etc/fstab
UUID=7e52ecef-fcd5-4767-a018-b78c85d5be0e /                      xfs       defaults        0 0
UUID=3c1d9414-9115-43ba-84fb-401472776367 /boot                  ext4      defaults        1 2
UUID=e97181be-696b-47c9-8c42-5c539598cea4 /data                  xfs       defaults        0 0
UUID=2d32ba3e-4ff7-4df6-bd34-748c877c1bda none                   swap      defaults        0 0

3、处理/etc/fstab路径,使用sed命令取出其目录名和基名

[root@centos8 ~]# echo "/etc/fstab" |sed -r 's#(^/.*/)([^/]+/?)#\1#'    #取目录名
/etc/
[root@centos8 ~]# echo "/etc/fstab" |sed -r 's#(^/.*/)([^/]+/?)#\2#'    #取基名
fstab