>/usr/bin : Most user commands</A
></H2
><DIV
CLASS="SECTION"
><H3
CLASS="SECTION"
><A
NAME="PURPOSE20"
>Purpose</A
></H3
><P
>This is the primary directory of executable commands on the
system.</P
></DIV
><DIV
CLASS="SECTION"
><HR><H3
CLASS="SECTION"
><A
NAME="SPECIFICOPTIONS11"
>Specific Options</A
></H3
><P
>The following directories, or symbolic links to directories,
must be in <TT
CLASS="FILENAME"
>/usr/bin</TT
>, if the corresponding
subsystem is installed:</P
><DIV
CLASS="INFORMALTABLE"
><P
></P
><A
NAME="AEN1313"
></A
><TABLE
BORDER="0"
FRAME="void"
CLASS="CALSTABLE"
><COL><COL><THEAD
><TR
><TH
>Directory</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="FILENAME"
>mh</TT
></TD
><TD
>Commands for the MH mail handling system (optional)</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
><P
><TT
CLASS="FILENAME"
>/usr/bin/X11</TT
> must be a symlink to
<TT
CLASS="FILENAME"
>/usr/X11R6/bin</TT
> if the latter exists.</P
><P
>The following files, or symbolic links to files, must be in
<TT
CLASS="FILENAME"
>/usr/bin</TT
>, if the corresponding subsystem is
installed:</P
><DIV
CLASS="INFORMALTABLE"
><P
></P
><A
NAME="AEN1329"
></A
><TABLE
BORDER="0"
FRAME="void"
CLASS="CALSTABLE"
><COL><COL><THEAD
><TR
><TH
>Command</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><B
CLASS="COMMAND"
>perl</B
></TD
><TD
>The Practical Extraction and Report Language (optional)</TD
></TR
><TR
><TD
><B
CLASS="COMMAND"
>python</B
></TD
><TD
>The Python interpreted language (optional)</TD
></TR
><TR
><TD
><B
CLASS="COMMAND"
>tclsh</B
></TD
><TD
>Simple shell containing Tcl interpreter (optional)</TD
></TR
><TR
><TD
><B
CLASS="COMMAND"
>wish</B
></TD
><TD
>Simple Tcl/Tk windowing shell (optional)</TD
></TR
><TR
><TD
><B
CLASS="COMMAND"
>expect</B
></TD
><TD
>Program for interactive dialog (optional)</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
><DIV
CLASS="TIP"
><P
></P
><TABLE
CLASS="TIP"
WIDTH="100%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="tip.gif"
HSPACE="5"
ALT="Tip"></TD
><TH
ALIGN="LEFT"
VALIGN="CENTER"
><B
>Rationale</B
></TH
></TR
><TR
><TD
> </TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>Because shell script interpreters (invoked with
<TT
CLASS="FILENAME"
>#!<path></TT
> on the first line of a shell
script) cannot rely on a path, it is advantageous to standardize their
locations. The Bourne shell and C-shell interpreters are already
fixed in <TT
CLASS="FILENAME"
>/bin</TT
>, but Perl, Python, and Tcl are
often found in many different places. They may be symlinks to the
physical location of the shell interpreters. </P
></TD
></TR
></TABLE
></DIV
></DIV
></DIV
><DIV
CLASS="SECTION"
><HR><H2
CLASS="SECTION"
><A
NAME="USRINCLUDEDIRECTORYFORSTANDARDINCLU"
>/usr/include : Directory for standard include files.</A
></H2
><DIV
CLASS="SECTION"
><H3
CLASS="SECTION"
><A
NAME="PURPOSE21"
>Purpose</A
></H3
><P
>This is where all of the system's general-use include files for the C
programming language should be placed.</P
></DIV
><DIV
CLASS="SECTION"
><HR><H3
CLASS="SECTION"
><A
NAME="SPECIFICOPTIONS12"
>Specific Options</A
></H3
><P
>The following directories, or symbolic links to directories,
must be in <TT
CLASS="FILENAME"
>/usr/include</TT
>, if the corresponding
subsystem is installed:</P
><DIV
CLASS="INFORMALTABLE"
><P
></P
><A
NAME="AEN1370"
></A
><TABLE
BORDER="0"
FRAME="void"
CLASS="CALSTABLE"
><COL><COL><THEAD
><TR
><TH
>Directory</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
>bsd</TD
><TD
>BSD compatibility include files (optional)</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
><P
>The symbolic link <TT
CLASS="FILENAME"
>/usr/include/X11</TT
> must
link to <TT
CLASS="FILENAME"
>/usr/X11R6/include/X11</TT
> if the latter
exists.</P
></DIV
></DIV
><DIV
CLASS="SECTION"
><HR><H2
CLASS="SECTION"
><A
NAME="USRLIBLIBRARIESFORPROGRAMMINGANDPA"
>/usr/lib : Libraries for programming and packages</A
></H2
><DIV
CLASS="SECTION"
><H3
CLASS="SECTION"
><A
NAME="PURPOSE22"
>Purpose</A
></H3
><P
><TT
CLASS="FILENAME"
>/usr/lib</TT
> includes object files, libraries,
and internal binaries that are not intended to be executed directly by
users or shell scripts.
<A
NAME="AEN1389"
HREF="#FTN.AEN1389"
><SPAN
CLASS="footnote"
>[22]</SPAN
></A
></P
><P
>Applications may use a single subdirectory under
<TT
CLASS="FILENAME"
>/usr/lib</TT
>. If an application uses a subdirectory,
all architecture-dependent data exclusively used by the application
must be placed within that subdirectory.
<A
NAME="AEN1394"
HREF="#FTN.AEN1394"
><SPAN
CLASS="footnote"
>[23]</SPAN
></A
></P
></DIV
><DIV
CLASS="SECTION"
><HR><H3
CLASS="SECTION"
><A
NAME="SPECIFICOPTIONS13"
>Specific Options</A
></H3
><P
>For historical reasons, <B
CLASS="COMMAND"
>/usr/lib/sendmail</B
>
must be a symbolic link to <B
CLASS="COMMAND"
>/usr/sbin/sendmail</B
> if
the latter exists.
<A
NAME="AEN1402"
HREF="#FTN.AEN1402"
><SPAN
CLASS="footnote"
>[24]</SPAN
></A
></P
><P
>If <TT
CLASS="FILENAME"
>/lib/X11</TT
> exists,
<TT
CLASS="FILENAME"
>/usr/lib/X11</TT
> must be a symbolic link to
<TT
CLASS="FILENAME"
>/lib/X11</TT
>, or to whatever
<TT
CLASS="FILENAME"
>/lib/X11</TT
> is a symbolic link to.
<A
NAME="AEN1418"
HREF="#FTN.AEN1418"
><SPAN
CLASS="footnote"
>[25]</SPAN
></A
></P
></DIV
></DIV
><DIV
CLASS="SECTION"
><HR><H2
CLASS="SECTION"
><A
NAME="USRLIBLTQUALGTALTERNATEFORMATLIBRARI"
>/usr/lib<qual> : Alternate format libraries (optional)</A
></H2
><DIV
CLASS="SECTION"
><H3
CLASS="SECTION"
><A
NAME="PURPOSE23"
>Purpose</A
></H3
><P
><TT
CLASS="FILENAME"
>/usr/lib<qual></TT
> performs the same role as <TT
CLASS="FILENAME"
>/usr/lib</TT
> for an
alternate binary format, except that the symbolic links
<TT
CLASS="FILENAME"
>/usr/lib<qual>/sendmail</TT
> and <TT
CLASS="FILENAME"
>/usr/lib<qual>/X11</TT
> are not required.
<A
NAME="AEN1435"
HREF="#FTN.AEN1435"
><SPAN
CLASS="footnote"
>[26]</SPAN
></A
></P
></DIV
><DIV
CLASS="SECTION"
><HR><H3
CLASS="SECTION"
><A
NAME="USRLOCALLOCALHIERARCHY"
>/usr/local : Local hierarchy</A
></H3
><DIV
CLASS="SECTION"
><H4
CLASS="SECTION"
><A
NAME="PURPOSE24"
>Purpose</A
></H4
><P
>The <TT