# man pages section 1: User Commands

Updated: Thursday, June 13, 2019

## filename (1t)

### Name

filename - File name conventions supported by Tcl commands

### Synopsis

Please see following description for synopsis

### Description

filename(1t)                 Tcl Built-In Commands                filename(1t)

______________________________________________________________________________

NAME
filename - File name conventions supported by Tcl commands
______________________________________________________________________________

INTRODUCTION
All  Tcl  commands  and  C procedures that take file names as arguments
expect the file names to be in one of three  forms,  depending  on  the
current  platform.   On  each  platform, Tcl supports file names in the
standard forms(s) for that platform.  In addition,  on  all  platforms,
Tcl supports a Unix-like syntax intended to provide a convenient way of
constructing simple file names.  However, scripts that are intended  to
be  portable  should  not  assume  a  particular  form  for file names.
Instead, portable scripts must use the file split and  file  join  com-
mands  to  manipulate  file  names  (see the file manual entry for more
details).

PATH TYPES
File names are grouped into three general types based on  the  starting
point  for  the  path used to specify the file: absolute, relative, and
volume-relative.  Absolute names are  completely  qualified,  giving  a
path to the file relative to a particular volume and the root directory
on that volume.  Relative names are unqualified, giving a path  to  the
file  relative to the current working directory.  Volume-relative names
are partially qualified, either giving the path relative  to  the  root
directory  on  the current volume, or relative to the current directory
of the specified volume.  The file pathtype  command  can  be  used  to
determine the type of a given path.

PATH SYNTAX
The  rules  for  native  names  depend on the value reported in the Tcl
platform element of the tcl_platform array:

Unix      On Unix and Apple MacOS X  platforms,  Tcl  uses  path  names
where  the  components  are separated by slashes.  Path names
may be relative or absolute, and file names may  contain  any
character other than slash.  The file names . and .. are spe-
cial and refer to the current directory and the parent of the
current  directory  respectively.   Multiple  adjacent  slash
characters are interpreted as a single separator.  Any number
of  trailing slash characters at the end of a path are simply
ignored, so the paths foo, foo/ and foo// are all  identical,
and  in particular foo/ does not necessarily mean a directory
is being referred.

The following  examples  illustrate  various  forms  of  path
names:

/              Absolute path to the root directory.

/etc/passwd    Absolute  path to the file named passwd in the
directory etc in the root directory.

.              Relative path to the current directory.

foo            Relative path to the file foo in  the  current
directory.

foo/bar        Relative path to the file bar in the directory
foo in the current directory.

../foo         Relative path to the file foo in the directory
above the current directory.

Windows   On Microsoft Windows platforms, Tcl supports both drive-rela-
tive and UNC style names.  Both / and \ may be used as direc-
tory separators in either type of name.  Drive-relative names
consist of an optional drive specifier followed by  an  abso-
lute  or  relative  path.   UNC paths follow the general form
\\servername\sharename\path\file, but must at the very  least
contain  the  server  and  share  components, i.e.  \\server-
name\sharename.  In both forms, the file names . and  ..  are
special  and refer to the current directory and the parent of
the current directory respectively.  The  following  examples
illustrate various forms of path names:

\\Host\share/file
Absolute UNC path to a file called file in the
root directory of the export  point  share  on
the host Host.  Note that repeated use of file
dirname on this path will  give  //Host/share,
and will never give just //Host.

c:foo          Volume-relative path to a file foo in the cur-
rent directory on drive c.

c:/foo         Absolute path to a file foo in the root direc-
tory of drive c.

foo\bar        Relative  path to a file bar in the foo direc-
tory in the current directory on  the  current
volume.

\foo           Volume-relative path to a file foo in the root
directory of the current volume.

\\foo          Volume-relative path to a file foo in the root
directory  of the current volume.  This is not
a valid UNC path, so the  assumption  is  that
the extra backslashes are superfluous.

TILDE SUBSTITUTION
In  addition  to the file name rules described above, Tcl also supports
csh-style tilde substitution.  If a file name starts with a tilde, then
the  file  name will be interpreted as if the first element is replaced
with the location of the home directory for the  given  user.   If  the
tilde  is  followed immediately by a separator, then the $HOME environ- ment variable is substituted. Otherwise the characters between the tilde and the next separator are taken as a user name, which is used to retrieve the user's home directory for substitution. This works on Unix, MacOS X and Windows (except very old releases). Old Windows platforms do not support tilde substitution when a user name follows the tilde. On these platforms, attempts to use a tilde followed by a user name will generate an error that the user does not exist when Tcl attempts to interpret that part of the path or otherwise access the file. The behaviour of these paths when not trying to interpret them is the same as on Unix. File names that have a tilde without a user name will be correctly substituted using the$HOME envi-
ronment variable, just like for Unix.

PORTABILITY ISSUES
Not all file systems are case sensitive, so scripts should  avoid  code
that  depends  on  the case of characters in a file name.  In addition,
the character sets allowed on different devices may differ, so  scripts
should  choose  file names that do not contain special characters like:
<>:?"/\|.  The safest approach is to use names consisting  of  alphanu-
meric  characters only.  Care should be taken with filenames which con-
tain spaces (common on Windows systems) and filenames where  the  back-
slash  is  the  directory  separator (Windows native path names).  Also
Windows 3.1 only supports file names with a root  of  no  more  than  8
characters and an extension of no more than 3 characters.

On Windows platforms there are file and path length restrictions.  Com-
plete paths or filenames longer than about 260 characters will lead  to
errors in most file operations.

Another Windows peculiarity is that any number of trailing dots "."  in
filenames are totally ignored, so, for example, attempts  to  create  a
file  or directory with a name "foo."  will result in the creation of a
file/directory with name "foo".  This fact is reflected in the  results
of  file  normalize.   Furthermore, a file name consisting only of dots
"........."  or dots with trailing characters ".....abc" is illegal.

ATTRIBUTES
See attributes(7) for descriptions of the following attributes:

+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
+---------------+------------------+
|Availability   | runtime/tcl-8    |
+---------------+------------------+
|Stability      | Uncommitted      |
+---------------+------------------+
file(n), glob(n)

KEYWORDS
current directory, absolute file name, relative file name, volume-rela-
tive file name, portability

NOTES
This     software     was    built    from    source    available    at
https://github.com/oracle/solaris-userland.   The  original   community