The difference between linux .and ..

. (dot, is "dot") (Recommended learning: linux operation and maintenance)

In the shell , users should all know that One dot represents the current directory, and two dots represent the upper directory.

CDPATH=.:~:/home:/home/web:/var:/usr/local

In the upstream CDPATH setting, the dot after the equal sign represents the current directory.

If the file name starts with dot, the file is a special file, and the -a option must be added to the ls command to display it. In addition, in regular expression, a dot represents matching one character.

In Linux, when . (dot) is placed at the parameter of a command that requires a directory name, it means "current directory"; and two dots (..) one immediately following the other Well, in the same scenario (i.e. when your command expects a directory of files) it means "the parent directory of the current directory".

The dot command in the Linux shell is completely equivalent to the source command.

[taoge@localhost Desktop]$ cat a.sh 
#! /bin/bash
echo "shell script"
export z="f(x) + f(y)"
[taoge@localhost Desktop]$ ./a.sh 
shell script
[taoge@localhost Desktop]$ echo $z

[taoge@localhost Desktop]$ . ./a.sh 
shell script
[taoge@localhost Desktop]$ echo $z
f(x) + f(y)
[taoge@localhost Desktop]$

We see that the point command is indeed equivalent to the source command. Please pay attention to ". ./a.sh". The first dot is a command, which is equivalent to source. The last dot is together with /. ./ represents the current directory. Moreover, be sure to pay attention to these two dots. There must be a space between them.

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