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Which is the duplicate file descriptor for dup2?
The close-on-exec flag ( FD_CLOEXEC; see fcntl (2)) for the duplicate descriptor is off. dup3 () is the same as dup2 (), except that: The caller can force the close-on-exec flag to be set for the new file descriptor by specifying O_CLOEXEC in flags.
How to return dup2 or dup3 in Linux?
(Linux only) This may be returned by dup2 () or dup3 () during a race condition with open (2) and dup (). The dup2 () or dup3 () call was interrupted by a signal; see signal (7) . ( dup3 ()) flags contain an invalid value. Or, oldfd was equal to newfd . The process already has the maximum number of file descriptors open and tried to open a new one.
How to duplicate a file descriptor in Linux?
The close-on-exec flag ( FD_CLOEXEC ; see fcntl (2)) for the duplicate descriptor is off. The dup2 () system call performs the same task as dup (), but instead of using the lowest-numbered unused file descriptor, it uses the file descriptor number specified in newfd .
How to set close on exec in DUP ( 2 )?
The caller can force the close-on-exec flag to be set for the new file descriptor by specifying O_CLOEXEC in flags. See the description of the same flag in open (2) for reasons why this may be useful.
Is there a limit to duplicating descriptors in BSD?
In BSD and GNU, the maximum is controlled by a resource limit that can be changed; see Limits on Resources, for more information about the RLIMIT_NOFILE limit. ENFILE is not a possible error code for dup2 because dup2 does not create a new opening of a file; duplicate descriptors do not count toward the limit which ENFILE indicates.
Which is the duplicating descriptor function in fcntl?
You can perform this operation using the fcntl function with the F_DUPFD command, but there are also convenient functions dup and dup2 for duplicating descriptors. The fcntl function and flags are declared in fcntl.h , while prototypes for dup and dup2 are in the header file unistd.h .