bsd/man/man2/pathconf.2

   1 .\"     $NetBSD: pathconf.2,v 1.2 1995/02/27 12:35:22 cgd Exp $
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  34 .\"     @(#)pathconf.2  8.1 (Berkeley) 6/4/93
  35 .\"
  36 .Dd June 4, 1993
  37 .Dt PATHCONF 2
  38 .Os BSD 4
  39 .Sh NAME
  40 .Nm fpathconf ,
  41 .Nm pathconf
  42 .Nd get configurable pathname variables
  43 .Sh SYNOPSIS
  44 .Fd #include <unistd.h>
  45 .Ft long
  46 .Fo fpathconf
  47 .Fa "int fildes"
  48 .Fa "int name"
  49 .Fc
  50 .Ft long
  51 .Fo pathconf
  52 .Fa "const char *path"
  53 .Fa "int name"
  54 .Fc
  55 .Sh DESCRIPTION
  56 .Pp
  57 The
  58 .Fn pathconf
  59 and
  60 .Fn fpathconf
  61 functions provides a method for applications to determine the current
  62 value of a configurable system limit or option variable associated
  63 with a pathname or file descriptor.
  64 .Pp
  65 For
  66 .Nm pathconf ,
  67 the
  68 .Fa path
  69 argument is the name of a file or directory.
  70 For
  71 .Nm fpathconf ,
  72 the
  73 .Fa fildes
  74 argument is an open file descriptor.
  75 The
  76 .Fa name
  77 argument specifies the system variable to be queried.
  78 Symbolic constants for each name value are found in the include file
  79 .Li <unistd.h> .
  80 .Pp
  81 The available values are as follows:
  82 .Pp
  83 .Bl -tag -width "123456"
  84 .Pp
  85 .It Li _PC_LINK_MAX
  86 The maximum file link count.
  87 .It Li _PC_MAX_CANON
  88 The maximum number of bytes in terminal canonical input line.
  89 .It Li _PC_MAX_INPUT
  90 The minimum maximum number of bytes for which space is available in
  91 a terminal input queue.
  92 .It Li _PC_NAME_MAX
  93 The maximum number of bytes in a file name.
  94 .It Li _PC_PATH_MAX
  95 The maximum number of bytes in a pathname.
  96 .It Li _PC_PIPE_BUF
  97 The maximum number of bytes which will be written atomically to a pipe.
  98 .It Li _PC_CHOWN_RESTRICTED
  99 Return 1 if appropriate privileges are required for the
 100 .Xr chown 2
 101 system call, otherwise 0.
 102 .It Li _PC_NO_TRUNC
 103 Return 1 if file names longer than KERN_NAME_MAX are truncated.
 104 .It Li _PC_VDISABLE
 105 Returns the terminal character disabling value.
 106 .It Li _PC_XATTR_SIZE_BITS
 107 Returns the number of bits used to store maximum extended
 108 attribute size in bytes.  For example, if the maximum
 109 attribute size supported by a file system is 128K, the
 110 value returned will be 18.  However a value 18 can mean
 111 that the maximum attribute size can be anywhere from
 112 (256KB - 1) to 128KB.  As a special case, the resource
 113 fork can have much larger size, and some file system
 114 specific extended attributes can have smaller and preset
 115 size; for example, Finder Info is always 32 bytes.
 116 .It Li _PC_MIN_HOLE_SIZE
 117 If a file system supports the reporting of holes (see
 118 .Xr lseek 2 ) ,
 119 .Fn pathconf
 120 and
 121 .Fn fpathconf
 122 return a positive number that represents the minimum hole size returned in
 123 bytes.
 124 The offsets of holes returned will be aligned to this same value.
 125 A special value of 1 is returned if the file system does not specify the minimum
 126 hole size but still reports holes.
 127 .El
 128 .Sh RETURN VALUES
 129 If the call to
 130 .Nm pathconf
 131 or
 132 .Nm fpathconf
 133 is not successful, \-1 is returned and
 134 .Va errno
 135 is set appropriately.
 136 Otherwise, if the variable is associated with functionality that does
 137 not have a limit in the system, \-1 is returned and
 138 .Va errno
 139 is not modified.
 140 Otherwise, the current variable value is returned.
 141 .Sh ERRORS
 142 If any of the following conditions occur, the
 143 .Nm pathconf
 144 and
 145 .Nm fpathconf
 146 functions shall return -1 and set
 147 .Va errno
 148 to the corresponding value.
 149 .Bl -tag -width ENAMETOOLONGAA
 150 .\" ===========
 151 .It Bq Er EINVAL
 152 The value of the
 153 .Fa name
 154 argument is invalid.
 155 .\" ===========
 156 .It Bq Er EINVAL
 157 The implementation does not support an association of the variable
 158 name with the associated file.
 159 .El
 160 .Pp
 161 .Fn pathconf
 162 will fail if:
 163 .Bl -tag -width ENAMETOOLONGAA
 164 .\" ===========
 165 .It Bq Er EACCES
 166 Search permission is denied for a component of the path prefix.
 167 .\" ===========
 168 .It Bq Er EIO
 169 An I/O error occurs while reading from or writing to the file system.
 170 .\" ===========
 171 .It Bq Er ELOOP
 172 Too many symbolic links are encountered in translating the pathname.
 173 This is taken to be indicative of a looping symbolic link.
 174 .\" ===========
 175 .It Bq Er ENAMETOOLONG
 176 A component of a pathname exceeded 255 characters,
 177 or an entire path name exceeded 1023 characters.
 178 .\" ===========
 179 .It Bq Er ENOENT
 180 The named file does not exist.
 181 .\" ===========
 182 .It Bq Er ENOTDIR
 183 A component of the path prefix is not a directory.
 184 .El
 185 .Pp
 186 .Bl -tag -width ENAMETOOLONGAA
 187 .Fn fpathconf
 188 will fail if:
 189 .\" ===========
 190 .It Bq Er EBADF
 191 .Fa fildes
 192 is not a valid open file descriptor.
 193 .\" ===========
 194 .It Bq Er EIO
 195 An I/O error occurs while reading from or writing to the file system.
 196 .El
 197 .Sh SEE ALSO
 198 .Xr sysctl 3
 199 .Sh HISTORY
 200 The
 201 .Nm pathconf
 202 and
 203 .Nm fpathconf
 204 functions first appeared in 4.4BSD.