dup2

Implemented in Antinomie 0.7.0 · Syscall list

Synopsis

long dup2(unsigned int oldfd, unsigned int newfd);

Number (x86-64)	33
ABI	common
Kernel entry point	sys_dup2

This is the raw kernel prototype from the pinned Linux 6.12.94 schema, not the libc wrapper.

Description

Duplicates a file descriptor onto a specific number, closing that number first if it was open.

Arguments

Name	Type	Meaning
oldfd (arg0)	unsigned int	File descriptor to duplicate.
newfd (arg1)	unsigned int	Descriptor number to duplicate onto.

Return value

On success: the new descriptor number.

In an Antinomie trace the Return column and the ret filter field show the raw kernel return value. On failure that is the negative errno, for example -2 for ENOENT, not the -1 plus errno that the libc wrapper gives. syscall.errno holds the positive errno and syscall.success is false.

Common errors

Raw return	Name	Meaning
-9	EBADF	A file descriptor is not valid for this operation.

Man page

dup2(2) on man7.org

Captured by Antinomie

Coverage mark: Implemented. All arguments are plain values, recorded as the raw argument words at entry. There is no pointee to copy and no known gap.

Every call is recorded as an Entry record (the six argument words and the pointees copied at entry) and an Exit record (the return value and the pointees copied at exit).

Arguments

Argument	When	How	Recorded field key	Condition
oldfd (arg0)	Entry	raw scalar word	args.0, args.oldfd
newfd (arg1)	Entry	raw scalar word	args.1, args.newfd

Filter fields

• Result: ret, syscall.errno, syscall.success, syscall.duration_ns.
• Argument words: args.oldfd (arg0), args.newfd (arg1); args.0 to args.5 by position.

See Syscall Trace filter for the full syntax.

For what the capture statuses mean, see Capture statuses. For what is never recorded, see Known gaps.