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File Descriptors - How many?

Posted on 1998-07-17
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Last Modified: 2010-04-21
I have a C++ program that is running on a unix machine.  I need to find out exactly how many file descriptors I have left.  I have a lot of socket connections opened and reading the output.  I am running into problems with some of the file descriptors I get a "Bad File Number".  I would like to exactly how many I have left.  Any ideas?

Is there a way to find out how many file descriptors I have left for the entire system as well as how many per process?
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Question by:sgrobins
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Expert Comment

by:ozo
ID: 2008862
#include <stdio.h>
define NFILE FOPEN_MAX
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Expert Comment

by:ozo
ID: 2008863
#include <sys/resource.h>
struct rlimit rl;
getrlimit(RLIMIT_NOFILE,&rl);

#include <ulimit.h>
limit=ulimit(UL_GDESLIM);
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Author Comment

by:sgrobins
ID: 2008864
I am using the gerlimit and setrlimit to set the maximum file descriptors allowed in my program.  I have set it to 1024.  What I would like to do is as the program is running see how many file descriptors are in use.  Is this possible?
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Rajkumar_R earned 200 total points
ID: 2008865
See the man page for select ! You can set all the bits from 0 to 1024  and using the call select you can check how many is readable how many is writable ...etc ...which ever is suitable to your logic !
eg:-

fd_set myfd;
FD_ZERO(&stFDset);      

for (i=0; i< 1024;i++ )
     FD_SET(i,&myfd);  

then call the select first to check how many is readable ..and then next to see how many is writable or both at once !

Please let me know if you need more details !

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