1CHOWN(2)                   Linux Programmer's Manual                  CHOWN(2)
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NAME

6       chown, fchown, lchown, fchownat - change ownership of a file
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SYNOPSIS

9       #include <unistd.h>
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11       int chown(const char *pathname, uid_t owner, gid_t group);
12       int fchown(int fd, uid_t owner, gid_t group);
13       int lchown(const char *pathname, uid_t owner, gid_t group);
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15       #include <fcntl.h>           /* Definition of AT_* constants */
16       #include <unistd.h>
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18       int fchownat(int dirfd, const char *pathname,
19                    uid_t owner, gid_t group, int flags);
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21   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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23       fchown(), lchown():
24           /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
25               || _XOPEN_SOURCE >= 500
26               || /* Glibc <= 2.19: */ _BSD_SOURCE
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28       fchownat():
29           Since glibc 2.10:
30               _POSIX_C_SOURCE >= 200809L
31           Before glibc 2.10:
32               _ATFILE_SOURCE
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DESCRIPTION

35       These  system calls change the owner and group of a file.  The chown(),
36       fchown(), and lchown() system calls differ only  in  how  the  file  is
37       specified:
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39       * chown()  changes  the  ownership  of  the file specified by pathname,
40         which is dereferenced if it is a symbolic link.
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42       * fchown() changes the ownership of the file referred to  by  the  open
43         file descriptor fd.
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45       * lchown() is like chown(), but does not dereference symbolic links.
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47       Only  a  privileged  process (Linux: one with the CAP_CHOWN capability)
48       may change the owner of a file.  The owner of a  file  may  change  the
49       group  of  the  file  to  any group of which that owner is a member.  A
50       privileged process (Linux: with CAP_CHOWN) may change the  group  arbi‐
51       trarily.
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53       If the owner or group is specified as -1, then that ID is not changed.
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55       When the owner or group of an executable file is changed by an unprivi‐
56       leged user, the S_ISUID and S_ISGID mode bits are cleared.  POSIX  does
57       not specify whether this also should happen when root does the chown();
58       the Linux behavior depends on  the  kernel  version,  and  since  Linux
59       2.2.13,  root is treated like other users.  In case of a non-group-exe‐
60       cutable file (i.e., one for which the S_IXGRP bit is not set) the S_IS‐
61       GID bit indicates mandatory locking, and is not cleared by a chown().
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63       When the owner or group of an executable file is changed (by any user),
64       all capability sets for the file are cleared.
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66   fchownat()
67       The fchownat() system call operates in exactly the same way as chown(),
68       except for the differences described here.
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70       If  the  pathname given in pathname is relative, then it is interpreted
71       relative to the directory referred to  by  the  file  descriptor  dirfd
72       (rather  than  relative to the current working directory of the calling
73       process, as is done by chown() for a relative pathname).
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75       If pathname is relative and dirfd is the special value  AT_