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File name processing
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<H3 CLASS="subsection"><A NAME="htoc239">7.26</A> File name processing</H3><UL>
<LI><A HREF="gprolog049.html#toc192"><TT>absolute_file_name/2</TT></A>
<LI><A HREF="gprolog049.html#toc193"><TT>decompose_file_name/4</TT></A>
<LI><A HREF="gprolog049.html#toc194"><TT>prolog_file_name/2</TT></A>
</UL>
<A NAME="toc192"></A>
<H4 CLASS="subsubsection"><A NAME="htoc240">7.26.1</A> <TT>absolute_file_name/2</TT></H4>
<A NAME="absolute-file-name/2"></A>
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
absolute_file_name(+atom, atom)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>absolute_file_name(File1, File2)</TT> succeeds if <TT>File2</TT> is
the absolute pathname associated with the relative file name <TT>File1</TT>.
<TT>File1</TT> can contain <TT>$<I>VAR_NAME</I></TT> sub-strings. When
such a sub-string is encountered, it is expanded with the value of the
environment variable whose name is <I><TT>VAR_NAME</TT></I> if exists
(otherwise no expansion is done). <TT>File1</TT> can also begin with a
sub-string <TT>~<I>USER_NAME</I>/</TT>, this is expanded as the home
directory of the user <I><TT>USER_NAME</TT></I>. If
<I><TT>USER_NAME</TT></I> does not exist <TT>File1</TT> is an invalid
pathname. If no <I><TT>USER_NAME</TT></I> is given (i.e. <TT>File1</TT>
begins with <TT>~/</TT>) the <TT>~</TT> character is expanded as the
value of the environment variable <TT>HOME</TT>. If the <TT>HOME</TT>
variable is not defined <TT>File1</TT> is an invalid pathname. Relative
references to the current directory (<TT>/./</TT> sub-string) and to the
parent directory (<TT>/../</TT> sub-strings) are removed and no longer
appear in <TT>File2</TT>. <TT>File1</TT> is also invalid if it contains too
many <TT>/../</TT> consecutive sub-strings (i.e. parent directory relative
references). Finally if <TT>File1</TT> is <TT>user</TT> then <TT>File2</TT>
is also unified with <TT>user</TT> to allow this predicate to be called on
Prolog file names (since <TT>user</TT> in DEC-10 input/output predicates
denotes the current input/output stream). <BR>
<BR>
Most predicates using a file name implicitly call this predicate to obtain
the desired file, e.g. <TT>open/4</TT>. <BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File1</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File1</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, File1)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File2</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, File2)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File1</TT> is an atom but not a valid pathname</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(os_path, File1)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc193"></A>
<H4 CLASS="subsubsection"><A NAME="htoc241">7.26.2</A> <TT>decompose_file_name/4</TT></H4>
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
decompose_file_name(+atom, ?atom, ?atom, ?atom)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>decompose_file_name(File, Directory, Prefix, Suffix)</TT> decomposes
the pathname <TT>File</TT> and extracts the <TT>Directory</TT> part
(characters before the last <TT>/</TT>), the <TT>Prefix</TT> part
(characters after the last <TT>/</TT> and before the last <TT>.</TT> or
until the end if there is no suffix) and the <TT>Suffix</TT> part
(characters from the last <TT>.</TT> to the end of the string). <BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, File)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Directory</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, Directory)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Prefix</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, Prefix)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Suffix</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, Suffix)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc194"></A>
<H4 CLASS="subsubsection"><A NAME="htoc242">7.26.3</A> <TT>prolog_file_name/2</TT></H4>
<A NAME="prolog-file-name/2"></A>
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
prolog_file_name(+atom, ?atom)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>prolog_file_name(File1, File2)</TT> unifies <TT>File2</TT> with the
Prolog file name associated with <TT>File1</TT>. More precisely <TT>File2</TT>
is computed as follows:
<UL CLASS="itemize"><LI CLASS="li-itemize">if <TT>File1</TT> has a suffix or if it is <TT>user</TT> then
<TT>File2</TT> is unified with <TT>File1</TT>.<BR>
<BR>
<LI CLASS="li-itemize">else if the file whose name is <TT>File1</TT> + <TT>'.pl'</TT> exists
then <TT>File2</TT> is unified with this name.<BR>
<BR>
<LI CLASS="li-itemize">else if the file whose name is <TT>File1</TT> + <TT>'.pro'</TT> exists
then <TT>File2</TT> is unified with this name.<BR>
<BR>
<LI CLASS="li-itemize">else <TT>File2</TT> is unified with the name <TT>File1</TT> +
<TT>'.pl'</TT>.</UL>
This predicate uses <TT>absolute_file_name/2</TT> to check the existence
of a file (section <A HREF="#absolute-file-name/2">7.26.1</A>).<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File1</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File1</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, File1)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File2</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, File2)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>File1</TT> is an atom but not a valid pathname</TD>
<TD VALIGN=top ALIGN=center NOWRAP> </TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(os_path, File1)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
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Copyright (C) 1999-2007 Daniel Diaz
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