The difference between DOS batch CD and ~DP0

Problem description

Suppose we want to call the execution batch in the batch A.bat B.bat,b.bat need to know the B.bat's current location and execute Run.exe as follows:

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Directory structure//C://A. BAT//-program//b. bat//-run. exe//A.bat call "%cd%\program\b.bat"//B.bat "%cd%\run.exe"

Now, then, can we successfully execute Run.exe?

Problem analysis

Both%cd% and%~dp0 can be used to represent the current directory, but they are not the same in different usage scenarios:%cd% represents the current working directory (present working directory,variable); DP0 represents the full directory of the current batch file (the batch file ' s directory,fixed).

Let's take a look at the following example:

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Directory structure//C://-C. BAT//-program/D. BAT//C.bat call "%cd%\program\d.bat"//D.bat @ echo off Ech o cd =% cd% echo dp0 =%~dp0

Run D.bat directly, the result is

1 2	cd = C:\program Dp0 = C:\program\

Run C.bat directly, the result is

1 2	cd = C:\ Dp0 = C:\program\

As you can see from the results above: When executing D.bat, the current working directory is the directory of D.bat, and the current working directory is C.bat directory when the C.bat is executed, even after the d.bat is invoked, the working directory is still the C.bat directory.

Problem solving

Let's take a look at the problems mentioned in the description of the problem--can we successfully execute Run.exe?

The answer is: No. "%cd%\run.exe" means "C:\run.exe", not "C:\program\run.exe". So how to change it.

There are two types of scenarios:

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Plan A//change the current working directory//A.bat CD "%~dp0" Call "%cd%\program\b.bat"//B.bat CD "%~dp0" "%cd%\ Run.exe "//plan B//using%~DP0 directly//A.bat call"%~dp0program\b.bat "//B.bat"%~dp0run.exe "

Problem extension

In the above solution, plan a solves the problem by changing the current directory, and there is another problem, let's look at the following example:

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Directory structure//C://-program//F. BAT//D://E. BAT//Plan A//change to current working directory// E.bat CD "%~dp0" Call "C:\program\f.bat"//F.bat CD "%~dp0" "%cd%\run.exe"

Now that E.bat and F.bat are not in the same letter, switching from E.bat current working directory to f.bat directly using the CD is not possible and must be used:

1	cd/d "%~dp0"

This place is easy to neglect, remember not to make mistakes.

Summary of issues

Let's reiterate the difference between%~dp0 and%cd%,%cd% and%~dp0 can be used to represent the current directory, but they are not the same in different usage scenarios:%cd% represents the current working directory (present working directory,variable) %~DP0 represents the full directory of the current batch file (the batch file ' s directory,fixed).

From the current use of our situation, try to use%~DP0, do not recommend the use of%cd%, except for other requirements.

Summary

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