Dealing with files that are currently opened in a program

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5
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2answers
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Portability of file descriptor links

I've always wondered this but never took the time to find out, so I'll do so now - how portable is the usage shown here of either /proc/$$/fd/$N or /dev/fd/$N? I understand POSIX guarantees /dev/null, ...
29
votes
6answers
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Who's got the other end of this unix socketpair?

I want to determine which process has the other end of a UNIX socket. Specifically, I'm asking about one that was created with socketpair(), though the problem is the same for any UNIX socket. I ...
21
votes
2answers
10k views

/proc/PID/fd/X link number

In Linux, in /proc/PID/fd/X, the links for file descriptors that are pipes or sockets have a number, like: l-wx------ 1 user user 64 Mar 24 00:05 1 -> pipe:[6839] l-wx------ 1 user user 64 Mar 24 ...
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votes
4answers
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How can same fd in different processes point to the same file?

Say I have process 1 and process 2. Both have a file descriptor corresponding to the integer 4. In each process however the file descriptor 4 points to a totally different file in the Open File Table ...
27
votes
3answers
48k views

Find and remove large files that are open but have been deleted

How does one find large files that have been deleted but are still open in an application? How can one remove such a file, even though a process has it open? The situation is that we are running a ...
34
votes
1answer
33k views

ulimit: difference between hard and soft limits

What is the difference between hard and soft limits in ulimit? For number of open files, I have a soft limit of 1024 and a hard limit of 10240. It is possible to run programs opening more than 1024 ...
5
votes
0answers
105 views

How can different file descriptors point to the same file in open file table? [duplicate]

Possible Duplicate: How can same fd in different processes point to the same file? I have a hard time grasping the two ideas of File Descriptor Table and Open File Table. Open File Table ...
30
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3answers
40k views

Why is number of open files limited in Linux?

Right now, I know that: Find open files limit per process: ulimit -n Count all opened files by all process: lsof | wc -l Get maximum open files count allowd: cat /proc/sys/fs/file-max My ...
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2answers
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Why does process substitution result in a file called /dev/fd/63 which is a pipe?

I am trying to understand named pipes in the context of this particular example. I type <(ls -l) in my terminal and get the output as, bash: /dev/fd/63: Permission denied. If I type cat <(ls ...
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3answers
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Monitor what is being sent to /dev/null?

Just for fun: Is there a way to monitor/capture/dump whatever is being written to /dev/null? On Debian, or FreeBSD, if it matters, any other OS specific solutions are also welcome.
15
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2answers
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How do open files behave on linux systems?

I just renamed a log file to "foo.log.old", and assumed that the application will start writing a new logfile at "foo.log". I was surprised to discover that it tracked the logfile to its new name, and ...
12
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2answers
4k views

What happens when I close() a file descriptor?

I am trying to get the whole picture with file descriptors. Say I have process1 which initially has these file descriptors: _process1_ | | | 0 stdin | | 1 stdout | | 2 stderr | ...
7
votes
3answers
722 views

How can a log program continue to log to a deleted file?

From the Unix Power Tools, 3rd Edition: Instead of Removing a File, Empty It section: If an active process has the file open (not uncommon for log files), removing the file and creating a new ...
5
votes
2answers
709 views

Recover deleted file that is currently being written to

I started downloading a big file and accidently deleted it a while ago. I know how to get its current contents by cping /proc/<pid>/fd/<fd> but since the download is still in progress ...
13
votes
3answers
2k views

Where do open file handles go when they die?

What happens to the files that are deleted while they have a file handle open to them? I have been wondering this ever since I figured out I could delete a video file while it was playing in MPlayer ...
2
votes
1answer
127 views

Find out to which directory a process is writing?

This question is NOT a duplicate of this question Find out current working directory of a running process?, because the writing directory can be different from the working directory. For example, I ...
7
votes
2answers
5k views

How to find out which file is currently written by a process

My situation is that from time to time a specific process (in this case, it's Thunderbird) doesn't react to user input for a minute or so. I found out using iotop that during this time, it writes ...
3
votes
2answers
200 views

File permissions and saving

Let's say you open a file on which you have write permission. Meanwhile you change permissions and remove write permission while you still have the file open in some editor. What will happen if you ...
3
votes
2answers
489 views

Capturing new output after deleting the output file

I'm runnig a java server on Debian with this command: java -jar myapp.jar [args] >> log.txt Once I gzipped the log file to send it and then I realized the original file was gone, leaving me ...