UNLINK(2) Linux Manual Page

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Name
unlink - delete a name and possibly the file it refers to
Synopsis
#include <unistd.h>
int unlink(const char *pathname);
Description
unlink deletes a name from the filesystem. If that name was the last link to a file and no processes have the file open the file is deleted and the space it was using is made available for reuse.
If the name was the last link to a file but any processes still have the file open the file will remain in existence until the last file descriptor referring to it is closed.
If the name referred to a symbolic link the link is removed.
If the name referred to a socket, fifo or device the name for it is removed but processes which have the object open may continue to use it.
Return Value
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
Errors

EACCES

Write access to the directory containing pathname is not allowed for the process's effective uid, or one of the directories in pathname did not allow search (execute) permission.

EPERM or EACCES

The directory containing pathname has the sticky-bit (S_ISVTX) set and the process's effective uid is neither the uid of the file to be deleted nor that of the directory containing it.

EPERM (Linux only)

The filesystem does not allow unlinking of files.

EPERM

The system does not allow unlinking of directories, or unlinking of directories requires privileges that the current process doesn't have. (This is the POSIX prescribed error return.)

EISDIR

pathname refers to a directory. (This is the non-POSIX value returned by Linux since 2.1.132.)

EBUSY (not on Linux)

The file pathname cannot be unlinked because it is being used by the system or another process and the implementation considers this an error.

EFAULT

pathname points outside your accessible address space.

ENAMETOOLONG

pathname was too long.

ENOENT

A component in pathname does not exist or is a dangling symbolic link, or pathname is empty.

ENOTDIR

A component used as a directory in pathname is not, in fact, a directory.

ENOMEM

Insufficient kernel memory was available.

EROFS

pathname refers to a file on a read-only filesystem.

ELOOP

Too many symbolic links were encountered in translating pathname.

EIO

An I/O error occurred.

Conforming to
SVr4, SVID, POSIX, X/OPEN, 4.3BSD. SVr4 documents additional error conditions EINTR, EMULTIHOP, ETXTBSY, ENOLINK.
Bugs
Infelicities in the protocol underlying NFS can cause the unexpected disappearance of files which are still being used.
See Also
link(2) , rename(2) , open(2) , rmdir(2) , mknod(2) , mkfifo(3) , remove(3) , rm(1)