'''file readable''', a subcommand of [file], returns `1` if ''name''
is readable by the current user, and `0` otherwise.



** Synopsis **

    :   '''file readable''' ''name''



** Description **

When '''file readable''' returns `1`, it does not necessarily mean that
"`[open] ''file'' r" will succeed.  For example, '''file readable''' might
return `1`, but [open] fails because someone has a write lock. 

On NTFS volumes, '''file readable''' doesn't currently take account of the more
complex Windows user/group stuff, so can return the wrong value.  Code
contributions using `GetSecurityInfo()` much appreciated.

[RS] 2007-02-16:  Quick workaround:

======
proc file'readable name {
    set rc [catch {open $name} fp]
    if {$rc==0} {close $fp}
    expr {$rc==0}
}
======

----

[jdc] 2007-10-23: After upgrading from Tcl 8.4.9 to 8.4.16, I experienced
problems with '''file readable''' for file on a SMB mount. '''file readable''' always returns 0, unless the `others` have read privilege on the file.  Tcl 8.5b1 has the same behavior.

[HaO] 2015-02-19: confirming that the issue exists also in 8.6.3. See bug [https://core.tcl.tk/tcl/info/1613456fffffffff%|%1613456%|%].

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