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24
votes
2answers
1k views

Is it safe to move a file that's being appended to?

I have a node.js process that uses fs.appendFile to add lines to file.log. Only complete lines of about 40 chars per lines are appended, e.g. calls are like fs.appendFile("start-end"), not 2 calls ...
24
votes
1answer
22k 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 ...
22
votes
2answers
5k views

Who's got the other end of this unix socketpair?

I want to determine what process has the other end of a unix socket, that was created with socketpair(). I have a program parent which creates a socketpair(AF_UNIX, SOCK_STREAM, 0, fds), and fork()s. ...
20
votes
3answers
19k 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 ...
19
votes
4answers
6k views

How do I find out which processes are preventing unmounting of a device?

Sometimes, I would like to umount a usb device, but I get a drive is busy error. How do I find out which processes or programs are accessing the device?
16
votes
3answers
25k 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 ...
15
votes
2answers
7k 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 ...
15
votes
3answers
3k views

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.
14
votes
5answers
4k views

What is using this network socket?

I'm trying to use NTP to update the time on my machine. However, it gives me an error: host # ntpdate ntp1.example.org 10 Aug 12:38:50 ntpdate[7696]: the NTP socket is in use, exiting What does the ...
14
votes
2answers
3k views

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 ...
13
votes
2answers
868 views

How to find out what process is writing to STDOUT?

I have two instances of a process running. One of them is "frEAkIng oUT!" and printing errors non stop to STDOUT. I want to kill the broken process but I have to make sure I don't terminate the wrong ...
13
votes
2answers
1k views

How do I “cat and follow” a file?

A file is being sequentially downloaded by wget. If I start unpacking it with cat myfile.tar.bz2 | tar -xj, it may unpack correctly or fail with "Unexpected EOF", depending on what is faster. How to ...
13
votes
3answers
1k 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 ...
13
votes
1answer
4k views

How do I monitor opened files of a process in realtime?

I know I can view the open files of a process using lsof at that moment in time on my Linux machine. However, a process can open, alter and close a file so quickly that I won't be able to see it when ...
12
votes
2answers
3k 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 | ...
9
votes
4answers
4k views

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 ...
9
votes
3answers
32k views

Alternatives for “lsof” command?

In many cases "lsof" is not installed on the machines that with I have to work, but the "function" of lsof would be needed very much (ex. on AIX). :\ Are there any "lsof" like applications in the ...
9
votes
2answers
2k views

How to find out the file offset of an opened file?

My problem is that with lsof -p pid I can find out the list of opened file of a process whose process id is pid. But is there a way to find out the file offset of each accessed file ? Please give me ...
9
votes
6answers
2k views

How do I set a limit on the number of files Linux can have open?

I plan to run a Java app using nohup ... &. The limit must apply to commands like this.
9
votes
1answer
138 views

Strategies for maintaining a reference to a file after it was moved or renamed?

I've had a mac at work lately, and was amazed to see that Xcode would still find my latest project after I renamed its folder and moved it someplace else. Now I understand that this is the result of ...
8
votes
2answers
4k views

See the STDOUT redirect of a running process

If I start an app with this command: /path/to/my/command >> /var/log/command.log And the command doesn't return, is there a way, from another prompt, to see what the STDOUT redirect is set ...
8
votes
3answers
1k views

rewrite existing file so that it gets replaced by new version atomically, only once fully written

I vaguely recall reading somewhere that there used to be, in some Unices a way to open an existing file for writing, with a flag that asked the kernel to use the old version (for other processes ...
7
votes
3answers
642 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 ...
7
votes
2answers
3k views

How do I tell a script to wait for a process to start accepting requests on a port?

I need a command that will wait for a process to start accepting requests on a specific port. Is there something in linux that does that? while (checkAlive -host localhost -port 13000 == false) ...
7
votes
1answer
759 views

file descriptors and /dev/fd

Are file descriptors unique across a process, or throughout the whole system. Because every file seems the use the same descriptor for stdin and stdout. Is there something special with these? How ...
7
votes
3answers
3k views

How to remove Notepad from the applications list?

After installing Wine, Notepad has became a default application to open unknown textual files by double click. I'd like to eliminate this behaviour and remove Notepad from the list of applications ...
6
votes
3answers
2k views

vim: How to switch to the directory listing from file view?

I have opened a dir vim some/dir. I can navigate within the tree, yet once I opened a file I wonder, how do I close the file view in order to go back to the directory listing to navigate to another ...
6
votes
2answers
3k views

Change default applications used by gnome-open, exo-open, xdg-open, gvfs-open and kde-open

How to change the applications associated with certain file-types for gnome-open, exo-open, xdg-open, gvfs-open and kde-open? Is there a way by editing config files or by a command-line command? Is ...
5
votes
3answers
451 views

tail -f, Determine if a file is no longer being written to [closed]

I am using tail -f to follow the growth of a log file. I am having trouble finding a way to detect if the process that is writing to the log file (when it crashes or is otherwise terminated) is no ...
5
votes
2answers
185 views

How does bash continue to work correctly when you move its working directory?

On Linux, I moved a directory to another directory using mv, and in another shell, my working directory happened to be the directory that was moved. I ran hg pull in that shell, and to my surprise, ...
5
votes
2answers
681 views

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, ...
5
votes
2answers
572 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 ...
5
votes
2answers
403 views

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 ...
5
votes
2answers
4k 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 ...
5
votes
3answers
2k views

What process is accessing a mounted filesystem sporadically?

I have a Solaris 10 server with autofs-mounted home dirs. On one server they are not unmounted after the 10 min timeout period. We've got AUTOMOUNT_TIMEOUT=600 in /etc/default/autofs, I ran automount ...
5
votes
1answer
802 views

Which command will open the default browser on a system to a given web page (terminal)?

Title says it all. Is there a way to open the default browser on a user's system to a specific page from within a Bash script, or other-language script?
5
votes
1answer
1k views

File descriptor limits are lost after a system reboot

I'm trying to increase the default file descriptor limits for processes on my system. Specifically I'm trying to get the limits to apply to the Condor daemon and its sub-processes when the machine ...
5
votes
1answer
381 views

How can I configure OpenBox session for opening files by mime type?

I've started using OpenBox and I really like it. But my chromium opens everything with firefox. Is there any fix for that? I'm looking for most lightweight solution, but also with easy and fast ...
5
votes
0answers
102 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 ...
4
votes
2answers
232 views

Emacs' file extension recognition

How do I get Emacs to recognize new file extensions? For example if I have a .c file and I open it in Emacs, I get the correct syntax highlighting for C, but if I have a .bob file format (which I know ...
4
votes
2answers
1k views

What is the referent of a file descriptor?

My understanding is that a file descriptor is an integer which is a key in the kernel's per-process mapping to objects such as open()ed files, pipes, sockets, etc. Is there a proper, short, and ...
4
votes
2answers
5k views

File descriptor linked to socket or pipe in proc [duplicate]

Possible Duplicate: /proc/PID/fd/X link number i have a question regarding the file descriptors and their linkage in the proc file system. I've observed that if i list the file descriptors ...
4
votes
1answer
76 views

How to make sure only one instance accessing the file at a time in a folder?

I have a shell script which will be executed by multiple instances and if an instance accessing a file and doing some operation how can I make sure other instances are not accessing the same file and ...
4
votes
2answers
293 views

Can I move a directory with open files?

Imagine a bunch of processes using a /home/user/logs directory. They have some logs open for a longer time.
4
votes
2answers
508 views

retrieving names of all open pdf files (in evince or otherwise)

I constantly have many PDF files open. These are usually downloaded using chrome and immediately opened using evince. I sometimes want to persist the state of all my open PDF files, so I could ...
4
votes
1answer
207 views

Using xdg-open for accessing network with normal explorer

I'm working with small network and I want to start network explorer from a terminal. When I tried to type xdg-open network:///server it opened google chrome and did nothing. I also tried to type ...
4
votes
3answers
1k views

Gedit opening an “Unsaved document” on opening files with mouse

When I open files by double-clicking a file with mouse I always get one additional "Unsaved Document X".. which is very annoying, because I have to close tham all, and click "Close without save" every ...
3
votes
3answers
79 views

Moving an open file to a different device

I have an application running that is generating a large (~200GB) output file, and takes about 35 hours to run (currently I'm about 12 hours in). The application just opens the file once then keeps it ...
3
votes
2answers
119 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
1answer
154 views

lsof doesn't return files open by the same user

Consider this simple scenario: I open a text file ~/textfile.txt with vim in one terminal (tried with both edit and read-only modes). In a different terminal, I run /usr/sbin/lsof ~/textfile.txt ...