Do not want a parent and its child process to share the same file descriptor table

Question

I open a file in program A. Its file descriptor is 3. Using fork followed by an execve I execute another program B, where I immediately open another file. This files descriptor is 4. If A and B was not sharing the file descriptor table then the file descriptor of file opened in B should have been 3. I need to create child processes not sharing the parents address space including open files.

Thanks a lot

score 2 · Accepted Answer · answered May 06 '11 at 04:27

2

The child doesn't share the same FD table, you simply forgot to close them in the child or mark them close-on-exec.

answered May 06 '11 at 04:27

Ignacio Vazquez-Abrams

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@lgnacio Thank You. But is there a way where the closing of files take place automatically before it is copied on new process creation. – Lipika Deka May 06 '11 at 04:54
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Mark them close-on-exec. http://stackoverflow.com/questions/1643304/how-to-set-close-on-exec-by-default/1644590#1644590 – Ignacio Vazquez-Abrams May 06 '11 at 04:59

score 1 · Answer 2 · answered May 06 '11 at 04:27

1

Close the file before execing the new process. Do that in the code between the fork() and exec().

answered May 06 '11 at 04:27

wallyk

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Thank You. But is there a way where the closing of files take place automatically before it is copied on new process creation. – Lipika Deka May 06 '11 at 04:54
Both answers are correct. I choose the other as it gives me two options. Thank you so much – Lipika Deka May 06 '11 at 04:56

Do not want a parent and its child process to share the same file descriptor table

2 Answers2