Why does Linux (including Mac system) execute instructions Add./??

For example, now to execute hive commands under $hive_home/bin to start hive, the order of execution for this instruction is as follows:

1 Find Path First

1.1 If $hive_home/bin is configured under the path path, there is no configuration under the path path.: You can execute hive directly under any path to start hive

1.2 If $hive_home/bin is not configured under the path path, it is not possible to execute hive instructions on any path only $hive_home/bin execute hive instructions

2 If there is no path, then look for:

2.1 If the path in/etc/profile is configured as follows: *:

Path=.:$JAVA _home/bin: $HADOOP _home/sbin: $HADOOP _home/bin: $SCALA _home/bin: $PATH

When used, you need to write the command name in the $hive_home/bin directory, such as HIVE to run

2.2 If the path in/etc/profile is configured as follows: None •:

Path= $JAVA _home/bin: $HADOOP _home/sbin: $HADOOP _home/bin: $SCALA _home/bin: $PATH

When used, it needs to be written in the $hive_home/bin directory ./hive to run

Why does Linux (including Mac system) execute instructions Add./??