Basic knowledge of shell
Self-built calibration time yum install-y ntp uses ntpdate time.fudan.edu.cn to calibrate time
Some of the most common uses of date in scripts:
Date +% F xxxx-xx-xx
Date +% T xx:xx:xx
Date +% Y prints the year in four-digit format
Date +% y prints the year in two-digit format
Date +% m month
Date + d date
Date +% H hours
Date +% M minutes
Date +% S seconds
Date +% s timestamp
Date +% w week, if the result shows 0, it means Sunday
Sometimes a day's date is used in the script: date-d "- 2 days" +% F
Define the format of the variable as the variable name = the value of the variable. You need to add the'$'symbol when referencing the variable in the script, which is consistent with the custom variable described earlier in shell.
Mathematical calculations should be enclosed in [] and with a'$'on the outside.
-lt (less than),-gt (greater than),-le (less than or equal to),-ge (greater than or equal to),-eq (equal to),-ne (not equal).
Read-p "Please input a number:" x
Read-p "Please input another number:" y
Sum=$ [$xylene roomy]
Echo "The sum of the two numbers is: $sum"
The read command is used in such a place to interact with the user, taking the string entered by the user as the value of the variable. The script execution process is as follows:
There is a $0, but it represents the name of the script itself.
If judgment statement; then
Command
Fi
If judgment statement; then
Command
Else
Command
Fi
(a) appears in if1.sh
