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Closing open file descriptors from /proc/pid/fd

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# 8  
Old 09-26-2011
If you means exec 5>&- you close the file descriptor #5 opened by your shell (if it was opened or nothing happens).
Last edited by rbatte1; 01-17-2017 at 07:56 AM..
# 9  
Old 09-26-2011
Quote:
Originally Posted by alpha_romeo
hi ygemici,

thanks for the suggestions Smilie . But i don't want to end the process. the process is a 24*7 running application. i shouldn't kill it.

I need to only close certain open file descriptors.

regards
romeo
if your process always works,why do you need close the opened files belong to your process?
if you want to close fd ın your script you can use this
test still fd is open?
Code:
lsof -a -d3|grep $$

and or you can use like this..
Code:
# ./chkfd filetest

-- chkfd code for 3fd(u)--
Code:
#!/bin/bash
exec 3<> $1
echo "3.FD is opened now.."
lsof -a -d3|grep $$
exec 3>&-
if [[ $(lsof -a -d3|grep $$|grep -v pipe) = "" ]] ; then
echo -e "\n3.FD is closed successfully" ;
else echo -e "\n3.FD maybe is still open, check your script code"
lsof -a -d3|grep $$
fi

# 10  
Old 09-26-2011
ygemici,

so exec 3>&- works.. thanks Smilie.. that answers my question.

i want to close the fds because there are too many open fds in the process and that is causing performance issues. I know it needs to be addressed in application and this is only a work around to close the fds from shell. i am looking for a temporary fix only.

Thanks all for your inputs
# 11  
Old 09-26-2011
Quote:
Originally Posted by alpha_romeo
yazu,

what will happen if i attempt to do a 5>&- from /proc/pid/fd ??.. will the fd not be closed ?

regards
romeo
you cann't/mustn't close fds belong to any process that opened fds( in -> /proc/PID/fd) by with `FDN>&-` command.For this with safely,you must kill the process..

But if you cannot kill it and you are sure what will be happened or wıll be not happened after close fds then you can execute these(below comms/calls) but I dont recommend this way for this job.
Code:
# ls -1 /proc/PID/fd ##(find fds)

Code:
gdb --pid PID #(attach process by debugger)
.......
.......
(gdb) p close(1) 
(gdb) p close(2) 
......
(gdb) p close(X) 
detach
quit

Code:
p close (1) --> print & close(syscall) the "FD 1" belong to PID
....


regards
ygemici
This User Gave Thanks to ygemici For This Post:
alpha_romeo
# 12  
Old 09-27-2011
thanks ygemici , it matches my requirements
# 13  
Old 09-29-2011
Quote:
Originally Posted by ygemici
you cann't/mustn't close fds belong to any process that opened fds( in -> /proc/PID/fd) by with `FDN>&-` command.For this with safely,you must kill the process..

But if you cannot kill it and you are sure what will be happened or wıll be not happened after close fds then you can execute these(below comms/calls) but I dont recommend this way for this job.
Code:
# ls -1 /proc/PID/fd ##(find fds)

Code:
gdb --pid PID #(attach process by debugger)
.......
.......
(gdb) p close(1) 
(gdb) p close(2) 
......
(gdb) p close(X) 
detach
quit

Code:
p close (1) --> print & close(syscall) the "FD 1" belong to PID
....


regards
ygemici
Hey,

I am triggering the gdb from script like:
gdb -command=file -p pid

it is running but saying hit return to continue.

how can i give gdb command so that it is ran as a silent command with out need for any user input ??
# 14  
Old 09-29-2011
You have got a really poorly designed application if you have to go in and close file handles in the manner you describe.

Why not fix the application?
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