One Linux command per day (--which) command

Leave yesterday's, to yesterday, today, you will start again.

OK, in the first stage we learned the operation commands of the file directory:

1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Ls	Cd	Pwd	Mkdir	Rm	RmDir	Mv	Cp	Touch	Cat	nl	More	Less	Head	Tail

Next we will learn the file Lookup command:

1	2	3	4
which	Whereis	Locate	Find (Exec/xargs)

Words don't say much, which walk up:

Which viewing the location of an executable file

Whereis viewing the location of a file

Locate to view file locations with a database

Find actual search hard disk query file name

The purpose of the which command is to search for the location of a system command in the path specified by the path variable, and to return the first search result, that is, by using the which command, you can see whether a system command exists, and which command is executed at which point.

1. Command format:

which executable file name

2. Command function:

The which instruction searches for the location of a system command in the path specified by the path variable, and returns the first search result.

3. Command parameters:

-n Specifies the length of the file name, which must be greater than or equal to the longest file name in all files.

-P is the same as the-n parameter, but the path to the file is included here.

-W Specifies the width of the field at the output.

-V Displays version information.

4. Usage examples:

Example 1: Finding files, displaying command paths

Command:

which pwd it outputs a path/bin/pwd, which is to search for a running document based on the directory within the path variable configured by the user, so the commands found for different path configurations are certainly not the same.

Example 2: Use which to find which

Command:

Which which it will output two paths: Alias Which= ' Alias | /usr/bin/which--tty-only--read-alias--show-dot--show-tilde '

/usr/bin/which

One of these two aliases. This is called a "command alias", and if a command has alias, which will print out its alias and path.

Example 3: Find the CD command

Command:

which CD

Output a bunch:/usr/bin/which:no CD in (PATH)

In this case, the CD command was not found because the CD command is not in the search scope, it is a bash built in command ~, but which is searched from PATH. All cannot be found.

One Linux command per day (--which) command