bsd/man/man2/chmod.2

   1 .\"     $NetBSD: chmod.2,v 1.7 1995/02/27 12:32:06 cgd Exp $
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  34 .\"     @(#)chmod.2     8.1 (Berkeley) 6/4/93
  35 .\"
  36 .Dd June 4, 1993
  37 .Dt CHMOD 2
  38 .Os BSD 4
  39 .Sh NAME
  40 .Nm chmod ,
  41 .Nm fchmod
  42 .Nd change mode of file
  43 .Sh SYNOPSIS
  44 .Fd #include <sys/types.h>
  45 .Fd #include <sys/stat.h>
  46 .Ft int
  47 .Fo chmod
  48 .Fa "const char *path"
  49 .Fa "mode_t mode"
  50 .Fc
  51 .Ft int
  52 .Fo fchmod
  53 .Fa "int fildes"
  54 .Fa "mode_t mode"
  55 .Fc
  56 .Sh DESCRIPTION
  57 The function
  58 .Fn chmod
  59 sets the file permission bits
  60 of the file
  61 specified by the pathname
  62 .Fa path
  63 to
  64 .Fa mode .
  65 .Fn Fchmod
  66 sets the permission bits of the specified
  67 file descriptor
  68 .Fa fildes .
  69 .Fn Chmod
  70 verifies that the process owner (user) either owns
  71 the file specified by
  72 .Fa path
  73 (or
  74 .Fa fildes ) ,
  75 or
  76 is the super-user.
  77 A mode is created from
  78 .Em or'd
  79 permission bit masks
  80 defined in
  81 .Aq Pa sys/stat.h :
  82 .Bd -literal -offset indent -compact
  83 #define S_IRWXU 0000700    /* RWX mask for owner */
  84 #define S_IRUSR 0000400    /* R for owner */
  85 #define S_IWUSR 0000200    /* W for owner */
  86 #define S_IXUSR 0000100    /* X for owner */
  87
  88 #define S_IRWXG 0000070    /* RWX mask for group */
  89 #define S_IRGRP 0000040    /* R for group */
  90 #define S_IWGRP 0000020    /* W for group */
  91 #define S_IXGRP 0000010    /* X for group */
  92
  93 #define S_IRWXO 0000007    /* RWX mask for other */
  94 #define S_IROTH 0000004    /* R for other */
  95 #define S_IWOTH 0000002    /* W for other */
  96 #define S_IXOTH 0000001    /* X for other */
  97
  98 #define S_ISUID 0004000    /* set user id on execution */
  99 #define S_ISGID 0002000    /* set group id on execution */
 100 #define S_ISVTX 0001000    /* save swapped text even after use */
 101 .Ed
 102 .Pp
 103 The
 104 .Dv ISVTX
 105 (the
 106 .Em sticky bit )
 107 indicates to the system which executable files are shareable (the
 108 default) and the system maintains the program text of the files
 109 in the swap area. The sticky bit may only be set by the super user
 110 on shareable executable files.
 111 .Pp
 112 If mode
 113 .Dv ISVTX
 114 (the `sticky bit') is set on a directory,
 115 an unprivileged user may not delete or rename
 116 files of other users in that directory. The sticky bit may be
 117 set by any user on a directory which the user owns or has appropriate
 118 permissions.
 119 For more details of the properties of the sticky bit, see
 120 .Xr sticky 8 .
 121 .Pp
 122 Writing or changing the owner of a file
 123 turns off the set-user-id and set-group-id bits
 124 unless the user is the super-user.
 125 This makes the system somewhat more secure
 126 by protecting set-user-id (set-group-id) files
 127 from remaining set-user-id (set-group-id) if they are modified,
 128 at the expense of a degree of compatibility.
 129 .Sh RETURN VALUES
 130 Upon successful completion, a value of 0 is returned.
 131 Otherwise, a value of -1 is returned and
 132 .Va errno
 133 is set to indicate the error.
 134 .Sh ERRORS
 135 The
 136 .Fn chmod
 137 system call will fail and the file mode will be unchanged if:
 138 .Bl -tag -width Er
 139 .\" ==========
 140 .It Bq Er EACCES
 141 Search permission is denied for a component of the path prefix.
 142 .\" ==========
 143 .It Bq Er EFAULT
 144 .Fa Path
 145 points outside the process's allocated address space.
 146 .\" ==========
 147 .It Bq Er EINTR
 148 Its execution was interrupted by a signal.
 149 .\" ==========
 150 .It Bq Er EIO
 151 An I/O error occurred while reading from or writing to the file system.
 152 .\" ==========
 153 .It Bq Er ELOOP
 154 Too many symbolic links were encountered in translating the pathname.
 155 This is taken to be indicative of a looping symbolic link.
 156 .\" ==========
 157 .It Bq Er ENAMETOOLONG
 158 A component of a pathname exceeded
 159 .Dv {NAME_MAX}
 160 characters, or an entire path name exceeded
 161 .Dv {PATH_MAX}
 162 characters.
 163 .\" ==========
 164 .It Bq Er ENOENT
 165 The named file does not exist.
 166 .\" ==========
 167 .It Bq Er ENOTDIR
 168 A component of the path prefix is not a directory.
 169 .\" ==========
 170 .It Bq Er EPERM
 171 The effective user ID does not match the owner of the file and
 172 the effective user ID is not the super-user.
 173 .\" ==========
 174 .It Bq Er EROFS
 175 The named file resides on a read-only file system.
 176 .El
 177 .Pp
 178 .Fn fchmod
 179 will fail if:
 180 .Bl -tag -width Er
 181 .\" ==========
 182 .It Bq Er EBADF
 183 .Fa fildes
 184 is not a valid file descriptor.
 185 .\" ==========
 186 .It Bq Er EINVAL
 187 .Fa fildes
 188 refers to a socket, not to a file.
 189 .\" ==========
 190 .It Bq Er EINVAL
 191 .Fa mode
 192 is not a valid file mode.
 193 .\" ==========
 194 .It Bq Er EINTR
 195 Its execution was interrupted by a signal.
 196 .\" ==========
 197 .It Bq Er EIO
 198 An I/O error occurred while reading from or writing to the file system.
 199 .\" ==========
 200 .It Bq Er EPERM
 201 The effective user ID does not match the owner of the file and
 202 the effective user ID is not the super-user.
 203 .\" ==========
 204 .It Bq Er EROFS
 205 The file resides on a read-only file system.
 206 .El
 207 .Sh LEGACY SYNOPSIS
 208 .Fd #include <sys/types.h>
 209 .Fd #include <sys/stat.h>
 210 .Pp
 211 The include file
 212 .In sys/types.h
 213 is necessary.
 214 .Sh SEE ALSO
 215 .Xr chmod 1 ,
 216 .Xr chown 2 ,
 217 .Xr open 2 ,
 218 .Xr stat 2 ,
 219 .Xr compat 5 ,
 220 .Xr sticky 8
 221 .Sh STANDARDS
 222 The
 223 .Fn chmod
 224 function is expected to conform to
 225 .St -p1003.1-88 .
 226 .Sh HISTORY
 227 The
 228 .Fn fchmod
 229 function call
 230 appeared in
 231 .Bx 4.2 .