Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com
Answertopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions
Privacy Policy

  




 

 

[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ]

5.8 Using Empty Commands

It is sometimes useful to define commands which do nothing. This is done simply by giving a command that consists of nothing but whitespace. For example:

 
target: ;

defines an empty command string for `target'. You could also use a line beginning with a tab character to define an empty command string, but this would be confusing because such a line looks empty.

You may be wondering why you would want to define a command string that does nothing. The only reason this is useful is to prevent a target from getting implicit commands (from implicit rules or the .DEFAULT special target; see section 10. Using Implicit Rules and see section Defining Last-Resort Default Rules).

You may be inclined to define empty command strings for targets that are not actual files, but only exist so that their prerequisites can be remade. However, this is not the best way to do that, because the prerequisites may not be remade properly if the target file actually does exist. See section Phony Targets, for a better way to do this.



 
 
  Published under the terms of the GNU General Public License Design by Interspire