[SOLVED] What is going on when fclose on FILE created with popen?

Issue

I just had to track down a very annoying bug where somebody used popen to open a pipe but closed the C FILE with fclose instead of pclose. On Linux this was no problem, but later this program was compiled on a OSX and things got awry.

So I wonder, what is going wrong when closing a pipe created by popen with fclose instead of pclose? And why was this working on linux, but not OSX/BSD?

Solution

It might only appear to work with Linux, e.g., you did not notice the problem. These questions list a few of the ways your program might malfunction (on a variety of platforms) when using fclose where pclose is needed:

• use fclose to pipe of popen is a serious bug?
• fclose()/pclose() may block on some file pointers

Those have several comments regarding the bad things that can happen (e.g., zombie processes) from not closing the pipe properly. In some cases, your program may open a pipe once, and then fail to open a pipe a second time.

Answered By - Thomas Dickey

Answer Checked By - Timothy Miller (WPSolving Admin)