path: root/doc/file.n

'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH file n 8.3 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
file \- Manipulate file names and attributes
.SH SYNOPSIS
\fBfile \fIoption\fR \fIname\fR ?\fIarg arg ...\fR?
.BE
.SH DESCRIPTION
.PP
This command provides several operations on a file's name or attributes.
\fIName\fR is the name of a file; if it starts with a tilde, then tilde
substitution is done before executing the command (see the manual entry for
\fBfilename\fR for details).  \fIOption\fR indicates what to do with the
file name.  Any unique abbreviation for \fIoption\fR is acceptable.  The
valid options are:
.TP
\fBfile atime \fIname\fR ?\fItime\fR?
.
Returns a decimal string giving the time at which file \fIname\fR was last
accessed.  If \fItime\fR is specified, it is an access time to set
for the file.  The time is measured in the standard POSIX fashion as
seconds from a fixed starting time (often January 1, 1970).  If the file
does not exist or its access time cannot be queried or set then an error is
generated.  On Windows, FAT file systems do not support access time.
.TP
\fBfile attributes \fIname\fR
.TP
\fBfile attributes \fIname\fR ?\fIoption\fR?
.TP
\fBfile attributes \fIname\fR ?\fIoption value option value...\fR?
.
This subcommand returns or sets platform-specific values associated
with a file. The first form returns a list of the platform-specific
options and their values. The second form returns the value for the
given option. The third form sets one or more of the values. The values
are as follows:
.RS
.PP
On Unix, \fB\-group\fR gets or sets the group name for the file. A
group id can be given to the command, but it returns a group name.
\fB\-owner\fR gets or sets the user name of the owner of the file. The
command returns the owner name, but the numerical id can be passed when
setting the owner. \fB\-permissions\fR retrieves or sets a file's
access permissions, using octal notation by default. This option also
provides limited support for setting permissions using the symbolic
notation accepted by the \fBchmod\fR command, following the form
[\fBugo\fR]?[[\fB+-=\fR][\fBrwxst\fR]\fB,\fR[...]]. Multiple permission
specifications may be given, separated by commas. E.g., \fBu+s,go-rw\fR
would set the setuid bit for a file's owner as well as remove read and
write permission for the file's group and other users. An
\fBls\fR-style string of the form \fBrwxrwxrwx\fR is also accepted but
must always be 9 characters long. E.g., \fBrwxr-xr-t\fR is equivalent
to \fB01755\fR. On versions of Unix supporting file flags,
\fB-readonly\fR returns the value of, or sets, or clears the readonly
attribute of a file, i.e., the user immutable flag (\fBuchg\fR) to the
\fBchflags\fR command.
.PP
On Windows, \fB\-archive\fR gives the value or sets or clears the
archive attribute of the file. \fB\-hidden\fR gives the value or sets
or clears the hidden attribute of the file. \fB\-longname\fR will
expand each path element to its long version. This attribute cannot be
set. \fB\-readonly\fR gives the value or sets or clears the readonly
attribute of the file. \fB\-shortname\fR gives a string where every
path element is replaced with its short (8.3) version of the
name. This attribute cannot be set. \fB\-system\fR gives or sets or
clears the value of the system attribute of the file.
.PP
On Mac OS X and Darwin, \fB\-creator\fR gives or sets the
Finder creator type of the file. \fB\-hidden\fR gives or sets or clears
the hidden attribute of the file. \fB\-readonly\fR gives or sets or
clears the readonly attribute of the file. \fB\-rsrclength\fR gives
the length of the resource fork of the file, this attribute can only be
set to the value 0, which results in the resource fork being stripped
off the file.
.RE
.TP
\fBfile channels\fR ?\fIpattern\fR?
.
If \fIpattern\fR is not specified, returns a list of names of all
registered open channels in this interpreter.  If \fIpattern\fR is
specified, only those names matching \fIpattern\fR are returned.  Matching
is determined using the same rules as for \fBstring match\fR.
.TP
\fBfile copy \fR?\fB\-force\fR? ?\fB\-\|\-\fR? \fIsource\fR \fItarget\fR
.TP
\fBfile copy \fR?\fB\-force\fR? ?\fB\-\|\-\fR? \fIsource\fR ?\fIsource\fR ...? \fItargetDir\fR
.
The first form makes a copy of the file or directory \fIsource\fR under
the pathname \fItarget\fR. If \fItarget\fR is an existing directory,
then the second form is used.  The second form makes a copy inside
\fItargetDir\fR of each \fIsource\fR file listed.  If a directory is
specified as a \fIsource\fR, then the contents of the directory will be
recursively copied into \fItargetDir\fR. Existing files will not be
overwritten unless the \fB\-force\fR option is specified (when Tcl will
also attempt to adjust permissions on the destination file or directory
if that is necessary to allow the copy to proceed).  When copying
within a single filesystem, \fIfile copy\fR will copy soft links (i.e.
the links themselves are copied, not the things they point to).  Trying
to overwrite a non-empty directory, overwrite a directory with a file,
or overwrite a file with a directory will all result in errors even if
\fB\-force\fR was specified.  Arguments are processed in the order
specified, halting at the first error, if any.  A \fB\-\|\-\fR marks
the end of switches; the argument following the \fB\-\|\-\fR will be
treated as a \fIsource\fR even if it starts with a \fB\-\fR.
.TP
\fBfile delete \fR?\fB\-force\fR? ?\fB\-\|\-\fR? ?\fIpathname\fR ... ?
.
Removes the file or directory specified by each \fIpathname\fR
argument.  Non-empty directories will be removed only if the
\fB\-force\fR option is specified.  When operating on symbolic links,
the links themselves will be deleted, not the objects they point to.
Trying to delete a non-existent file is not considered an error.
Trying to delete a read-only file will cause the file to be deleted,
even if the \fB\-force\fR flags is not specified.  If the \fB\-force\fR
option is specified on a directory, Tcl will attempt both to change
permissions and move the current directory
.QW pwd
out of the given path if that is necessary to allow the deletion to
proceed.  Arguments are processed in the order specified, halting at
the first error, if any.
A \fB\-\|\-\fR marks the end of switches; the argument following the
\fB\-\|\-\fR will be treated as a \fIpathname\fR even if it starts with
a \fB\-\fR.
.TP
\fBfile dirname \fIname\fR
Returns a name comprised of all of the path components in \fIname\fR
excluding the last element.  If \fIname\fR is a relative file name and
only contains one path element, then returns
.QW \fB.\fR .
If \fIname\fR refers to a root directory, then the root directory is
returned.  For example,
.RS
.PP
.CS
\fBfile dirname\fR c:/
.CE
.PP
returns \fBc:/\fR.
.PP
Note that tilde substitution will only be
performed if it is necessary to complete the command. For example,
.PP
.CS
\fBfile dirname\fR ~/src/foo.c
.CE
.PP
returns \fB~/src\fR, whereas
.PP
.CS
\fBfile dirname\fR ~
.CE
.PP
returns \fB/home\fR (or something similar).
.RE
.TP
\fBfile executable \fIname\fR
.
Returns \fB1\fR if file \fIname\fR is executable by the current user,
\fB0\fR otherwise. On Windows, which does not have an executable attribute,
the command treats all directories and any files with extensions
\fBexe\fR, \fBcom\fR, \fBcmd\fR or \fBbat\fR as executable.
.TP
\fBfile exists \fIname\fR
.
Returns \fB1\fR if file \fIname\fR exists and the current user has
search privileges for the directories leading to it, \fB0\fR otherwise.
.TP
\fBfile extension \fIname\fR
.
Returns all of the characters in \fIname\fR after and including the last
dot in the last element of \fIname\fR.  If there is no dot in the last
element of \fIname\fR then returns the empty string.
.TP
\fBfile home ?\fIusername\fR?
.VS "8.7, TIP 602"
If no argument is specified, the command returns the home directory
of the current user. This is generally the value of the \fB$HOME\fR
environment variable except that on Windows platforms backslashes
in the path are replaced by forward slashes. An error is raised if
the \fB$HOME\fR environment variable is not set.
.RS
.PP
If \fIusername\fR is specified, the command returns the home directory
configured in the system for the specified user. Note this may be
different than the value of the \fB$HOME\fR environment variable
even when \fIusername\fR corresponds to the current user. An error is
raised if the \fIusername\fR does not correspond to a user account
on the system.
.RE
.VE "8.7, TIP 602"
.TP
\fBfile isdirectory \fIname\fR
.
Returns \fB1\fR if file \fIname\fR is a directory, \fB0\fR otherwise.
.TP
\fBfile isfile \fIname\fR
.
Returns \fB1\fR if file \fIname\fR is a regular file, \fB0\fR otherwise.
.TP
\fBfile join \fIname\fR ?\fIname ...\fR?
.
Takes one or more file names and combines them, using the correct path
separator for the current platform.  If a particular \fIname\fR is
relative, then it will be joined to the previous file name argument.
Otherwise, any earlier arguments will be discarded, and joining will
proceed from the current argument.  For example,
.RS
.PP
.CS
\fBfile join\fR a b /foo bar
.CE
.PP
returns \fB/foo/bar\fR.
.PP
Note that any of the names can contain separators, and that the result
is always canonical for the current platform: \fB/\fR for Unix and
Windows.
.RE
.TP
\fBfile link\fR ?\fI\-linktype\fR? \fIlinkName\fR ?\fItarget\fR?
.
If only one argument is given, that argument is assumed to be
\fIlinkName\fR, and this command returns the value of the link given by
\fIlinkName\fR (i.e. the name of the file it points to).  If
\fIlinkName\fR is not a link or its value cannot be read (as, for example,
seems to be the case with hard links, which look just like ordinary
files), then an error is returned.
.RS
.PP
If 2 arguments are given, then these are assumed to be \fIlinkName\fR
and \fItarget\fR. If \fIlinkName\fR already exists, or if \fItarget\fR
does not exist, an error will be returned.  Otherwise, Tcl creates a new
link called \fIlinkName\fR which points to the existing filesystem
object at \fItarget\fR (which is also the returned value), where the
type of the link is platform-specific (on Unix a symbolic link will be
the default).  This is useful for the case where the user wishes to
create a link in a cross-platform way, and does not care what type of
link is created.
.PP
If the user wishes to make a link of a specific type only, (and signal an
error if for some reason that is not possible), then the optional
\fI\-linktype\fR argument should be given.  Accepted values for
\fI\-linktype\fR are
.QW \fB\-symbolic\fR
and
.QW \fB\-hard\fR .
.PP
On Unix, symbolic links can be made to relative paths, and those paths
must be relative to the actual \fIlinkName\fR's location (not to the
cwd), but on all other platforms where relative links are not supported,
target paths will always be converted to absolute, normalized form
before the link is created (and therefore relative paths are interpreted
as relative to the cwd).  Furthermore,
.QW ~user
paths are always expanded
to absolute form.  When creating links on filesystems that either do not
support any links, or do not support the specific type requested, an
error message will be returned.  Most Unix platforms support both
symbolic and hard links (the latter for files only). Windows
supports symbolic directory links and hard file links on NTFS drives.
.RE
.TP
\fBfile lstat \fIname varName\fR
.
Same as \fBstat\fR option (see below) except uses the \fIlstat\fR
kernel call instead of \fIstat\fR.  This means that if \fIname\fR
refers to a symbolic link the information returned in \fIvarName\fR
is for the link rather than the file it refers to.  On systems that
do not support symbolic links this option behaves exactly the same
as the \fBstat\fR option.
.TP
\fBfile mkdir\fR ?\fIdir\fR ...?
.
Creates each directory specified.  For each pathname \fIdir\fR specified,
this command will create all non-existing parent directories as
well as \fIdir\fR itself.  If an existing directory is specified, then
no action is taken and no error is returned.  Trying to overwrite an existing
file with a directory will result in an error.  Arguments are processed in
the order specified, halting at the first error, if any.
.TP
\fBfile mtime \fIname\fR ?\fItime\fR?
.
Returns a decimal string giving the time at which file \fIname\fR was last
modified.  If \fItime\fR is specified, it is a modification time to set for
the file (equivalent to Unix \fBtouch\fR).  The time is measured in the
standard POSIX fashion as seconds from a fixed starting time (often January
1, 1970).  If the file does not exist or its modified time cannot be queried
or set then an error is generated.
.TP
\fBfile nativename \fIname\fR
.
Returns the platform-specific name of the file. This is useful if the
filename is needed to pass to a platform-specific call, such as to a
subprocess via \fBexec\fR under Windows (see \fBEXAMPLES\fR below).
.TP
\fBfile normalize \fIname\fR
.
Returns a unique normalized path representation for the file-system
object (file, directory, link, etc), whose string value can be used as a
unique identifier for it.  A normalized path is an absolute path which has
all
.QW ../
and
.QW ./
removed.  Also it is one which is in the
.QW standard
format for the native platform.  On Unix, this means the segments
leading up to the path must be free of symbolic links/aliases (but the
very last path component may be a symbolic link), and on Windows it also
means we want the long form with that form's case-dependence (which
gives us a unique, case-dependent path).  The one exception concerning the
last link in the path is necessary, because Tcl or the user may wish to
operate on the actual symbolic link itself (for example \fBfile delete\fR,
\fBfile rename\fR, \fBfile copy\fR are defined to operate on symbolic
links, not on the things that they point to).
.TP
\fBfile owned \fIname\fR
.
Returns \fB1\fR if file \fIname\fR is owned by the current user, \fB0\fR
otherwise.
.TP
\fBfile pathtype \fIname\fR
.
Returns one of \fBabsolute\fR, \fBrelative\fR, \fBvolumerelative\fR. If
\fIname\fR refers to a specific file on a specific volume, the path type will
be \fBabsolute\fR. If \fIname\fR refers to a file relative to the current
working directory, then the path type will be \fBrelative\fR. If \fIname\fR
refers to a file relative to the current working directory on a specified
volume, or to a specific file on the current working volume, then the path
type is \fBvolumerelative\fR.
.TP
\fBfile readable \fIname\fR
.
Returns \fB1\fR if file \fIname\fR is readable by the current user,
\fB0\fR otherwise.
.TP
\fBfile readlink \fIname\fR
.
Returns the value of the symbolic link given by \fIname\fR (i.e. the name
of the file it points to).  If \fIname\fR is not a symbolic link or its
value cannot be read, then an error is returned.  On systems that do not
support symbolic links this option is undefined.
.TP
\fBfile rename \fR?\fB\-force\fR? ?\fB\-\|\-\fR? \fIsource\fR \fItarget\fR
.TP
\fBfile rename \fR?\fB\-force\fR? ?\fB\-\|\-\fR? \fIsource\fR ?\fIsource\fR ...? \fItargetDir\fR
.
The first form takes the file or directory specified by pathname
\fIsource\fR and renames it to \fItarget\fR, moving the file if the
pathname \fItarget\fR specifies a name in a different directory.  If
\fItarget\fR is an existing directory, then the second form is used.
The second form moves each \fIsource\fR file or directory into the
directory \fItargetDir\fR. Existing files will not be overwritten
unless the \fB\-force\fR option is specified.  When operating inside a
single filesystem, Tcl will rename symbolic links rather than the
things that they point to.  Trying to overwrite a non-empty directory,
overwrite a directory with a file, or a file with a directory will all
result in errors.  Arguments are processed in the order specified,
halting at the first error, if any.  A \fB\-\|\-\fR marks the end of
switches; the argument following the \fB\-\|\-\fR will be treated as a
\fIsource\fR even if it starts with a \fB\-\fR.
.TP
\fBfile rootname \fIname\fR
.
Returns all of the characters in \fIname\fR up to but not including the
last
.QW .
character in the last component of name.  If the last
component of \fIname\fR does not contain a dot, then returns \fIname\fR.
.TP
\fBfile separator\fR ?\fIname\fR?
.
If no argument is given, returns the character which is used to separate
path segments for native files on this platform.  If a path is given,
the filesystem responsible for that path is asked to return its
separator character.  If no file system accepts \fIname\fR, an error
is generated.
.TP
\fBfile size \fIname\fR
.
Returns a decimal string giving the size of file \fIname\fR in bytes.  If
the file does not exist or its size cannot be queried then an error is
generated.
.TP
\fBfile split \fIname\fR
.
Returns a list whose elements are the path components in \fIname\fR.  The
first element of the list will have the same path type as \fIname\fR.
All other elements will be relative.  Path separators will be discarded
unless they are needed to ensure that an element is unambiguously relative.
For example, under Unix
.RS
.PP
.CS
\fBfile split\fR /foo/~bar/baz
.CE
.PP
returns
.QW \fB/\0\0foo\0\0./~bar\0\0baz\fR
to ensure that later commands
that use the third component do not attempt to perform tilde
substitution.
.RE
.TP
\fBfile stat \fIname varName\fR
.
Invokes the \fBstat\fR kernel call on \fIname\fR, and uses the variable
given by \fIvarName\fR to hold information returned from the kernel call.
\fIVarName\fR is treated as an array variable, and the following elements
of that variable are set: \fBatime\fR, \fBctime\fR, \fBdev\fR, \fBgid\fR,
\fBino\fR, \fBmode\fR, \fBmtime\fR, \fBnlink\fR, \fBsize\fR, \fBtype\fR,
\fBuid\fR.  Each element except \fBtype\fR is a decimal string with the
value of the corresponding field from the \fBstat\fR return structure;
see the manual entry for \fBstat\fR for details on the meanings of the
values.  The \fBtype\fR element gives the type of the file in the same
form returned by the command \fBfile type\fR.  This command returns an
empty string.
.TP
\fBfile system \fIname\fR
.
Returns a list of one or two elements, the first of which is the name of
the filesystem to use for the file, and the second, if given, an
arbitrary string representing the filesystem-specific nature or type of
the location within that filesystem.  If a filesystem only supports one
type of file, the second element may not be supplied.  For example the
native files have a first element
.QW native ,
and a second element which when given is a platform-specific type name
for the file's system (e.g.
.QW NTFS ,
.QW FAT ,
on Windows).  A generic virtual file system might return
the list
.QW "vfs ftp"
to represent a file on a remote ftp site mounted as a
virtual filesystem through an extension called
.QW vfs .
If the file does not belong to any filesystem, an error is generated.
.TP
\fBfile tail \fIname\fR
.
Returns all of the characters in the last filesystem component of
\fIname\fR.  Any trailing directory separator in \fIname\fR is ignored.
If \fIname\fR contains no separators then returns \fIname\fR.  So,
\fBfile tail a/b\fR, \fBfile tail a/b/\fR and \fBfile tail b\fR all
return \fBb\fR.
.TP
\fBfile tempdir\fR ?\fItemplate\fR?
.VS "8.7, TIP 431"
Creates a temporary directory (guaranteed to be newly created and writable by
the current script) and returns its name. If \fItemplate\fR is given, it
specifies one of or both of the existing directory (on a filesystem controlled
by the operating system) to contain the temporary directory, and the base part
of the directory name; it is considered to have the location of the directory
if there is a directory separator in the name, and the base part is everything
after the last directory separator (if non-empty).  The default containing
directory is determined by system-specific operations, and the default base
name prefix is
.QW \fBtcl\fR .
.RS
.PP
The following output is typical and illustrative; the actual output will vary
between platforms:
.PP
.CS
% \fBfile tempdir\fR
/var/tmp/tcl_u0kuy5
 % \fBfile tempdir\fR /tmp/myapp
/tmp/myapp_8o7r9L
% \fBfile tempdir\fR /tmp/
/tmp/tcl_1mOJHD
% \fBfile tempdir\fR myapp
/var/tmp/myapp_0ihS0n
.CE
.RE
.VE "8.7, TIP 431"
.TP
\fBfile tempfile\fR ?\fInameVar\fR? ?\fItemplate\fR?
'\" TIP #210
Creates a temporary file and returns a read-write channel opened on that file.
If the \fInameVar\fR is given, it specifies a variable that the name of the
temporary file will be written into; if absent, Tcl will attempt to arrange
for the temporary file to be deleted once it is no longer required. If the
\fItemplate\fR is present, it specifies parts of the template of the filename
to use when creating it (such as the directory, base-name or extension) though
some platforms may ignore some or all of these parts and use a built-in
default instead.
.RS
.PP
Note that temporary files are \fIonly\fR ever created on the native
filesystem. As such, they can be relied upon to be used with operating-system
native APIs and external programs that require a filename.
.RE
.TP
\fBfile tildeexpand \fIname\fR
.VS "8.7, TIP 602"
Returns the result of performing tilde substitution on \fIname\fR. If the name
begins 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 path separator, the \fBHOME\fR
environment 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.  An error is raised if the
\fBHOME\fR environment variable or user does not exist.
.RS
.PP
If the file name does not begin with a tilde, it is returned unmodified.
.RE
.VE "8.7, TIP 602"
.TP
\fBfile type \fIname\fR
.
Returns a string giving the type of file \fIname\fR, which will be one of
\fBfile\fR, \fBdirectory\fR, \fBcharacterSpecial\fR, \fBblockSpecial\fR,
\fBfifo\fR, \fBlink\fR, or \fBsocket\fR.
.TP
\fBfile volumes\fR
.
Returns the absolute paths to the volumes mounted on the system, as a
proper Tcl list.  Without any virtual filesystems mounted as root
volumes, on UNIX, the command will always return
.QW / ,
since all filesystems are locally mounted.
On Windows, it will return a list of the available local drives
(e.g.
.QW "a:/ c:/" ).
If any virtual filesystem has mounted additional
volumes, they will be in the returned list.
.TP
\fBfile writable \fIname\fR
.
Returns \fB1\fR if file \fIname\fR is writable by the current user,
\fB0\fR otherwise.
.SH "PORTABILITY ISSUES"
.TP
\fBUnix\fR\0\0\0\0\0\0\0
.
These commands always operate using the real user and group identifiers,
not the effective ones.
.TP
\fBWindows\fR\0\0\0\0
.
The \fBfile owned\fR subcommand uses the user identifier (SID) of
the process token, not the thread token which may be impersonating
some other user.
.SH EXAMPLES
.PP
This procedure shows how to search for C files in a given directory
that have a correspondingly-named object file in the current
directory:
.PP
.CS
proc findMatchingCFiles {dir} {
    set files {}
    switch $::tcl_platform(platform) {
        windows {
            set ext .obj
        }
        unix {
           set ext .o
        }
    }
    foreach file [glob \-nocomplain \-directory $dir *.c] {
        set objectFile [\fBfile tail\fR [\fBfile rootname\fR $file]]$ext
        if {[\fBfile exists\fR $objectFile]} {
            lappend files $file
        }
    }
    return $files
}
.CE
.PP
Rename a file and leave a symbolic link pointing from the old location
to the new place:
.PP
.CS
set oldName foobar.txt
set newName foo/bar.txt
# Make sure that where we're going to move to exists...
if {![\fBfile isdirectory\fR [\fBfile dirname\fR $newName]]} {
    \fBfile mkdir\fR [\fBfile dirname\fR $newName]
}
\fBfile rename\fR $oldName $newName
\fBfile link\fR \-symbolic $oldName $newName
.CE
.PP
On Windows, a file can be
.QW started
easily enough (equivalent to double-clicking on it in the Explorer
interface) but the name passed to the operating system must be in
native format:
.PP
.CS
exec {*}[auto_execok start] {} [\fBfile nativename\fR ~/example.txt]
.CE
.SH "SEE ALSO"
filename(n), open(n), close(n), eof(n), gets(n), tell(n), seek(n),
fblocked(n), flush(n)
.SH KEYWORDS
attributes, copy files, delete files, directory, file, move files, name,
rename files, stat, user
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