Sed, regular expression of shell programming

1、 Show /etc/rc.d/rc.sysinit File with size insensitive h Beginning line ;

[[email protected] test]# grep -E "^[h|H]" /etc/rc.d/rc.sysinit

2、 Show /etc/passwd China and Israel sh The line at the end ;

[[email protected] test]# grep sh$ /etc/passwd

3、 Show /etc/fstab China and Israel # start , One or more whitespace characters followed by , And then it's followed by any non whitespace line ;

[[email protected] test]# grep "^#[[:space:]]\{1,\}[^[:space:]]" /etc/fstab
# /etc/fstab
# Created by anaconda on Sat Jul  9 04:36:11 2022
# 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.

4、 lookup /etc/rc.d/rc.local Contained in the “ With to Start with to ending ” Word serial of ;

[[email protected] test]# grep "\(to\).*\1" /etc/rc.d/rc.local
# In contrast to previous versions due to parallel execution during boot

5、 lookup /etc/inittab contains “ With s start , And d Ending words ” Pattern line ;

[[email protected] test]# grep "\<s[a-Z]*d\>" /etc/inittab
# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
# systemd uses 'targets' instead of runlevels. By default, there are two main targets:

6、 lookup ifconfig In the command result 1-255 Integer between ;

[[email protected] test]# ifconfig | grep -E "\<([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\>"
[[email protected] test]# ifconfig | grep -w "`seq 255`"
        inet 192.168.223.132  netmask 255.255.255.0  broadcast 192.168.223.255
        inet6 fe80::20c:29ff:fe8f:6df2  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:8f:6d:f2  txqueuelen 1000  (Ethernet)
        RX packets 14634  bytes 14380402 (13.7 MiB)
        TX packets 9060  bytes 724182 (707.2 KiB)
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        RX packets 12  bytes 1020 (1020.0 B)
        TX packets 12  bytes 1020 (1020.0 B)

7、 Show /var/log/secure The file contains “Failed” or “FAILED” The line of ;

[[email protected] test]# egrep "(Failed|FAILED)" /var/log/secure

8、 stay /etc/passwd Take out the default shell by bash The line of ;

[[email protected] test]# grep "bash" /etc/passwd
root:x:0:0:root:/root:/bin/bash
redhat:x:1000:1000:redhat:/home/redhat:/bin/bash
tom:x:1003:1003::/home/tom:/bin/bash
user1:x:1004:1004::/home/user1:/bin/bash
user2:x:1005:1005::/home/user2:/bin/bash
user3:x:1006:1006::/home/user3:/bin/bash
user4:x:1007:1007::/home/user4:/bin/bash
user5:x:1008:1008::/home/user5:/bin/bash
user6:x:1009:1009::/home/user6:/bin/bash
user7:x:1010:1010::/home/user7:/bin/bash
user8:x:1011:1011::/home/user8:/bin/bash
user9:x:1012:1012::/home/user9:/bin/bash
user10:x:1013:1013::/home/user10:/bin/bash
user11:x:1014:1014::/home/user11:/bin/bash
user12:x:1015:1015::/home/user12:/bin/bash
user13:x:1016:1016::/home/user13:/bin/bash
user14:x:1017:1017::/home/user14:/bin/bash
user15:x:1018:1018::/home/user15:/bin/bash
user16:x:1019:1019::/home/user16:/bin/bash
user17:x:1020:1020::/home/user17:/bin/bash
user18:x:1021:1021::/home/user18:/bin/bash
user19:x:1022:1022::/home/user19:/bin/bash
user20:x:1023:1023::/home/user20:/bin/bash

9、 List... In long format /etc/ Directory to ns start 、.conf File information at the end ;

[[email protected] test]# ll /etc/ns*.conf
lrwxrwxrwx. 1 root root 29 Jul  9 12:47 /etc/nsswitch.conf -> /etc/authselect/nsswitch.conf

10、 Highlight passwd Colon in file , And the characters on both sides ;

[[email protected] test]# grep -E --color "(.(:.){1,}|.:+.)" /etc/passwd

1、 Delete /etc/grub2.conf All the white space characters at the beginning of the line that start with white space in the file

[[email protected] etc]# vim testgrub.conf
jdskjgfkllksllkldkjfl
    kjkdjjlas
   dksjkdjksjl
  fjkjdsjf
 kdjfjdskla
jdksjfkjksjlkf
   kfdsjlflmmflmdl
    dsjfjlsaksakkfldkkdkl
[[email protected] etc]# sed -r 's/^[[:space:]]//' /etc/testgrub.conf    
jdskjgfkllksllkldkjfl
   kjkdjjlas
  dksjkdjksjl
 fjkjdsjf
kdjfjdskla
jdksjfkjksjlkf
  kfdsjlflmmflmdl
   dsjfjlsaksakkfldkkdkl

2、 Delete /etc/fstab All # start , The first line of a line followed by at least one white space character # And white space characters

[[email protected] rc.d]# cat /etc/fstab
​
#
# /etc/fstab
# Created by anaconda on Sat Jul  9 04:36:11 2022
#
# 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=8e1cec7b-3876-430c-a34c-8c6c658ce96a /boot                   xfs     defaults        0 0
/dev/mapper/rhel-swap   none                    swap    defaults        0 0
/dev/sr0    /mnt    iso9660     defaults    0 0
​
[[email protected] test]# sed -r 's/^#[[:space:]]*//' /etc/fstab 
​
​
/etc/fstab
Created by anaconda on Sat Jul  9 04:36:11 2022
​
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=8e1cec7b-3876-430c-a34c-8c6c658ce96a /boot                   xfs     defaults        0 0
/dev/mapper/rhel-swap   none                    swap    defaults        0 0
/dev/sr0    /mnt    iso9660     defaults    0 0
​

3、 stay /root/install.log Add... At the beginning of each line # Number

[[email protected] test]# sed -r 's/^.*$/#&/' /root/install.sh

4、 stay /etc/fstab The document does not contain # The beginning of the first line increases # Number

[[email protected]host test]# sed -r 's/^[^\#]/#&/' /etc/fstab 
​
#
# /etc/fstab
# Created by anaconda on Sat Jul  9 04:36:11 2022
#
# 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=8e1cec7b-3876-430c-a34c-8c6c658ce96a /boot                   xfs     defaults        0 0
#/dev/mapper/rhel-swap   none                    swap    defaults        0 0
#/dev/sr0   /mnt    iso9660     defaults    0 0
​

5、 utilize sed Take out ifconfig In the command IPv4 Address

[[email protected] test]# ifconfig | sed -n 2p | sed -r "s/.*inet[[:space:]]*//" | sed -r "s/[[:space:]]*netmask.*//"
192.168.223.132

6、 Turn off the machine SELinux The function of

[[email protected] test]# sed -I 's#SELINUX=enforced#SELINUX=disabled#g'
[[email protected] test]# getenforce 
Disabled
​

7、 stay /etc/hosts Add content to the configuration file

[[email protected] test]# sed -i '1 i 1234567' /etc/hosts
[[email protected] test]# sed -i '$ a qwertyu' /etc/hosts
[[email protected] test]# cat /etc/hosts
1234567
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.223.132     www.ceshi.com
qwertyu