Test operation symbols in shell scripts and && | |

测试操作符 based on the modified time of the file

Common Test Operators	English name	Description
-F file	file	files exist and are normal files True, that is, test expressions are set
-d file	Direct Ory	file exists and is true for the catalog file, that is, the test expression is
-S file	size	file exists and the file size is not 0 true, that is, the test expression is established
-e file	exist	file exists as true, that is, the test expression is set
-r file	read	the file exists and is readable as true, that is, the test expression is set
-W file	write	file exists and can be written as true, that is, the test expression is established
-X file	executable	file exists and is executable as true, that is, the test expression is set
-L file	link	file exists and is true for linked file, that is, test expression established
fi-nt F2	newer than	file F1 is newer than file F2 is true, that is, the test expression is established. Based on the modified time of the file
f1-ot F2	older than	file F1 than file F2 old is true, that is, the test expression is established. Calculation of
&& with	operator

&& operators
Format: Command1 && Command2
&& the command on the Left (command 1) returns True (that is, returns 0, executed successfully) and the command (Command 2) on the right side of the,&& can be executed, in other words,"If this command succeeds && executes this command."
|| Operator
Format: Command1 | | Command2
|| is the opposite of &&. if | | The command on the left (Command1) did not execute successfully, then execute | | The command on the right (Command2), or in other words,"If this command fails to execute | | Then execute this command. "

Test operation symbols in shell scripts and && | |