HP 3000 Manuals HP 3000 Manuals
dup, dup2
Duplicates an open file descriptor.
Syntax
#include <unistd.h>
int dup (int fildes);
int dup2(iint fildes, int fildes2)
Parameters
fildes An open file descriptor.
Return Values
>=0 Success. A new file descriptor is returned.
-1 An error occurred. the open file descriptor is not
duplicated, and errno is set to indicate the error condition.
Description
The dup() and dup2 functions return the lowest numbered file descriptor
not currentely open by the calling process. The file descriptors
returned by dup() and dup2() refer to the same open file description as
fildes and share any locks.
The dup() and dup2() functions ignore file access permission bits when
attempting to duplicate an open file descriptor.
Implementation Considerations
Refer to the EEXCL and ESYSERR error descriptions below.
Signals generated for the calling process during execution of dup() re
deferred from delivery until completion of this function.
Errors
If an error occurs, errno is set to one of the following values:
EBADF CAUSE The parameter fildes is not a valid open file
descriptor.
ACTION Check to see if the value passed in fildes has been
altered or whether the file indicated by fildes was
ever opened.
EEXCL CAUSE The specified file descriptor is opened for exclusive
access.
ACTION Do not attempt to duplicate a file descriptor that is
opened for exclusive access.
EMFILE CAUSE The number of open files and directories would exceed
{OPEN_MAX}, the limit of opened files per process.
ACTION Check process limit in <limits.h>. Close a file.
ESYSERR CAUSE An operating system error has occurred that does not
map directly to any of the above errors.
ACTION Examine the MPE/iX error stack for the type of system
error.
See Also
close(), creat(), execl(), execv(), open(), POSIX.1 (Section 6.2.1)