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UNDELETE(2) System Calls Manual UNDELETE(2)

undelete — attempt to recover a deleted file

#include <unistd.h>

int
undelete(const char *path);

The () function attempts to recover the deleted file named by path. Currently, this works only when the named object is a whiteout in a union filesystem. The system call removes the whiteout causing any objects in a lower layer of the union stack to become visible once more.

Eventually, the undelete functionality may be expanded to other filesystems able to recover deleted files such as the log-structured filesystem.

Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

The undelete() succeeds unless:

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A component of the path prefix is not a directory.
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The pathname contains a character with the high-order bit set.
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A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
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The path does not reference a whiteout.
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The named whiteout does not exist.
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Search permission is denied for a component of the path prefix.
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Write permission is denied on the directory containing the name to be undeleted.
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Too many symbolic links were encountered in translating the pathname.
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The directory containing the name is marked sticky, and the containing directory is not owned by the effective user ID.
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An I/O error occurred while updating the directory entry.
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The name resides on a read-only file system.
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Path points outside the process's allocated address space.

unlink(2), mount_union(8)

An undelete function call first appeared in 4.4BSD-Lite.

BSD 4 October 18, 1994 UNDELETE(2)