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What is the file descriptor for standard input?
Stdin, stdout, and stderr
| Name | File descriptor | Abbreviation |
|---|---|---|
| Standard input | 0 | stdin |
| Standard output | 1 | stdout |
| Standard error | 2 | stderr |
Does every file have a file descriptor?
Every File has an associated number called File Descriptor (FD). Your screen also has a File Descriptor. When a program is executed the output is sent to File Descriptor of the screen, and you see program output on your monitor.
What is Cloexec?
2 Answers. 2. 84. It sets the close-on-exec flag for the file descriptor, which causes the file descriptor to be automatically (and atomically) closed when any of the exec -family functions succeed.
How to check if FD is a valid file descriptor?
fcntl (fd, F_GETFD) is the canonical cheapest way to check that fd is a valid open file descriptor. If you need to batch-check a lot, using poll with a zero timeout and the events member set to 0 and checking for POLLNVAL in revents after it returns is more efficient.
How to check if a given file descriptor is stored in a?
The descriptor is typically just a small integer like 6 and your libc can choose to reuse that number if you close the file and open a new one later. Instead, you should consider using dup () to copy the file descriptor.
How to test a file descriptor in Linux?
For Linux atleast, [ [ -e /dev/fd/$ {FD} ]] will do, where FD is the bash-variable that stores the FD you want to test. The command succeeds when FD is open, fails otherwise. The question is quite old – but anyway – why just do not use builtins?
How to get list of open file descriptors?
For a list of of open file descriptors. Add -l to see where they go. Open file descriptors can be found in /proc/ /fd. To list, for example, the open file descriptors of the current shell you can issue ls -l /proc/$$/fd which should give you something like: