mknod(2)

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

6       mknod - create a special or ordinary file
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SYNOPSIS

9       #include <sys/types.h>
10       #include <sys/stat.h>
11       #include <fcntl.h>
12       #include <unistd.h>
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14       int mknod(const char *pathname, mode_t mode, dev_t dev);
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DESCRIPTION

17       The system call mknod() creates a filesystem node (file, device special
18       file or named pipe) named pathname, with attributes specified  by  mode
19       and dev.
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21       The mode argument specifies both the permissions to use and the type of
22       node to be created.  It should be a combination (using bitwise  OR)  of
23       one  of  the  file  types  listed below and the permissions for the new
24       node.
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26       The permissions are modified by the process's umask in the  usual  way:
27       the permissions of the created node are (mode & ~umask).
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29       The  file  type  must  be  one of S_IFREG, S_IFCHR, S_IFBLK, S_IFIFO or
30       S_IFSOCK to specify a normal file (which will be created empty),  char‐
31       acter  special  file,  block  special  file, FIFO (named pipe), or Unix
32       domain socket, respectively.  (Zero file type  is  equivalent  to  type
33       S_IFREG.)
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35       If the file type is S_IFCHR or S_IFBLK then dev specifies the major and
36       minor numbers of the newly created device special file; otherwise it is
37       ignored.
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39       If pathname already exists, or is a symbolic link, this call fails with
40       an EEXIST error.
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42       The newly created node will be owned by the effective user  ID  of  the
43       process.  If the directory containing the node has the set-group-ID bit
44       set, or if the filesystem is mounted with BSD group semantics, the  new
45       node will inherit the group ownership from its parent directory; other‐
46       wise it will be owned by the effective group ID of the process.
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RETURN VALUE

49       mknod() returns zero on success, or -1 if an error occurred  (in  which
50       case, errno is set appropriately).
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ERRORS

53       EACCES The  parent  directory  does  not  allow write permission to the
54              process, or one of the directories in the path prefix  of  path‐
55              name  did  not  allow search permission.  (See also path_resolu‐
56              tion(2).)
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58       EEXIST pathname already exists.
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60       EFAULT pathname points outside your accessible address space.
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62       EINVAL mode requested creation of something other than a  normal  file,
63              device special file, FIFO or socket.
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65       ELOOP  Too many symbolic links were encountered in resolving pathname.
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67       ENAMETOOLONG
68              pathname was too long.
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70       ENOENT A  directory  component  in pathname does not exist or is a dan‐
71              gling symbolic link.
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73       ENOMEM Insufficient kernel memory was available.
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75       ENOSPC The device containing pathname has no room for the new node.
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77       ENOTDIR
78              A component used as a directory in pathname is not, in  fact,  a
79              directory.
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81       EPERM  mode  requested creation of something other than a regular file,
82              FIFO (named pipe), or Unix domain socket, and the caller is  not
83              privileged (Linux: does not have the CAP_MKNOD capability); also
84              returned if the filesystem containing pathname does not  support
85              the type of node requested.
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87       EROFS  pathname refers to a file on a read-only filesystem.
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CONFORMING TO

90       SVr4, 4.4BSD, POSIX.1-2001 (but see below).
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NOTES

93       POSIX.1-2001  says:  "The  only  portable use of mknod() is to create a
94       FIFO-special file. If mode is not S_IFIFO or dev is not 0, the behavior
95       of mknod() is unspecified."
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97       Under  Linux,  this  call  cannot  be  used to create directories.  One
98       should make directories with mkdir(2), and FIFOs with mkfifo(2).
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100       There are many infelicities in the protocol underlying  NFS.   Some  of
101       these affect mknod().
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