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What is the purpose of close function?
The close() function shall deallocate the file descriptor indicated by fildes. To deallocate means to make the file descriptor available for return by subsequent calls to open() or other functions that allocate file descriptors.
Why should I close a file?
(2) When writing to a file, the data may not be written to disk until the file is closed. When you say “output. write(…)”, the data is often cached in memory and doesn’t hit the hard drive until the file is closed. The longer you keep the file open, the greater the chance that you will lose data.
What are closed files?
A file containing records generated by a process that has been completed and to which additional information is not likely to be added; a cut-off file. A file to which access is not allowed.
Which is the correct way to close a file descriptor?
In that aspect, close is a bit like free: it is invalidating the value (file descriptor for close, pointer for free) passed to it. When possible, you could set the file descriptor to -1 (or some other invalid value) after a successful close (2), so code close (fd); fd = -1; for example.
What happens if file descriptor n is not specified?
If word evaluates to ‘-‘, file descriptor n, or standard output if n is not specified, is closed. Attempts to close a file descriptor that is not open shall not constitute an error. If word evaluates to something else, the behavior is unspecified. Note that neither specifies anything about how file descriptor n was opened originally.
When do you open a file descriptor in Bash?
In the bash tutorial I am reading, it says that if you open a file descriptor for reading, i.e. However, if you open a file descriptor for writing, it must be closed like this: Yet when I look on the internet, I see people opening files and then closing them with this: NOTE: when, according to the tutorial, they should be using exec 3<&1.
How to close a file descriptor in PID 1234?
For the process of pid 1234, use /proc/1234/fd/ & /proc/1234/fdinfo/ to understand its file descriptors and their table, and /proc/1234/maps & /proc/1234/smaps to understand its virtual address space. So if a called function close -s it, you should not use it anymore.