Conditional test statement
And: &&——A&&B——B will be executed only if A succeeds.
awk'{print $4}' Only column 4 will be kept
or:||——A||B——A failed, then B will be executed
:!—— The judgment result is reversed
$VSER: The variable that saves the current user name
Integer comparison operators
| -eq | Is it equal to |
|---|---|
| -born | Is not equal to |
| -gt | Is greater than |
| -lt | Is it less than |
| -the | Is it equal to or less than |
| -give | Is greater than or equal to |
String comparison operators
| = | Compare whether the string content is the same |
|---|---|
| != | Compare whether the string content is different |
| -with | Determine whether the string content is empty |
| -with | Determine whether the variable is used |
if statement
if: conditional test operation
the: command sequence
fi: end
vim host.sh——host: test whether the host is online
1, ping -c 4 i 0.3 -w 4 $1 &> /dev/null
[1] -c 4: try The number of times
[2] i 0.3: each data packet sending interval 0.3: interval time
[3]-w 4: sending timeout period
[4] &: case insensitive
[5]>: output redirection
[6]/dev /null: Linux black hole file
read: able to read the information entered by the user
-p: display certain user information to the user