1, define a command alias that is effective for all users, for example: lftps=’172.168.0.1/pub’
echo "alias lftps='172.168.0.1/pub'" >> /etc/bashrc && source /etc/bashrc
2, display all lines in the /etc/passwd file that do not end with /bin/bash
grep -v "/ bin/bash$" /etc/passwd
3, find the line containing two or three digits in the /etc/passwd file
grep "\<[0 -9]\{2,3\}\>" /etc/passwd
4, display the line starting with case s in the /proc/meminfo file, in three ways
grep -i'^s' /proc/meminfo
grep'^[sS]]' /proc/meminfo
grep -E'^(s|S)' /proc/meminfo
5, Use echo to output an absolute path, use egrep to take the path name type and execute the result of dirname /etc/passwd
echo "/a/b/c/d" | egrep -o ' .*/'
6 Find out the ip address in ifconfig, and require the result to display only the ip address
ifconfig | egrep -o'inet (addr:)?([0-9 ]*\.){3}[0-9]*' | egrep -o'([0-9]*\.){3}[0-9]*' | head -n 1
< p>7 Vim custom automatic indentation of 4 characters
cat >> /etc/vimrc << EOF
set ai
set tabstop=4
EOF
8 Write a script to realize automatic addition Three users, and calculate the sum of the uids of these three users
#!/bin/bash
#
sum_uid=0
for account in user1 user2 user3< br /> do
if id $account &> /dev/null
then echo "$account exists"
else
useradd $account
fi
uid=$(id -u $account )
sum_uid=$[$sum_uid+$uid]
done
echo "The sum of the UID of 3 users is $sum_uid"
9 find usage and common examples< /p>
fine [options] [Search start path] [Search condition] [Processing action]
-name file name search supports glob
-iname ignore case
Search by subordinate
-user USERNAME
-user groupname
-uid
-gid
-nouser finds files without an owner
-nogroup
finds file types
-type
f normal files
d directory file
l symbolic link file
b block device file
c character device file
p pipe file
s socket
combined search
and: -a
or: -o< br /> Non: -not,!
File size
-size [+|-]#unit
Commonly used unit: k MG
< br /> #unit: (#-1, #]
-#unit: [0-#-1 ]
+#unit: (#, infinity)< br /> Time
In days
-atime [+|-]# Visit
#: The past few days [#，#-1)
-# (# , 0] In the past #days
+# (00, #-1] How many days have passed
-mtime modification
-ctime modification
In minutes
-amin
-mmin
-cmin
Permission
-perm [+|-]mode
mode: exactly matches the mode
+mode: ugo group has one set of satisfaction
br /> -mode: Less than mode permission is sufficient
Processing action:
-print output to standard output default action
-ls
-delete delete
- fls /path The detailed information of the file searched is saved to the specified file.
-ok COMMAND {} \; Execute the command specified by COMMAND for each file found, and each operation is confirmed by the user.
-exec COMMANd {} \; Execute the command specified by COMMAND for each file found, no user confirmation is required for each operation