[Finish ch21 changes
John Goerzen <jgoerzen@complete.org>**20080708075258] {
hunk ./en/ch21-systems.xml 95
+      <para>
+        Is the <literal>filter (`notElem` [".", ".."])</literal> part
+        confusing?  That could got also be written as <literal>filter
+        (\c -> not $ elem c [".", ".."])</literal>.  The backticks in
+        this case effectively let us pass the second argument to
+        <literal>notElem</literal>; see <xref linkend="fp.infix"/> for
+        more information on backticks.
+      </para>
hunk ./en/ch21-systems.xml 149
-        the traditional POSIX epoch.  A &ClockTime; represents the number of
-        seconds since midnight the morning of January 1, 1970, UTC.  A
-        negative &ClockTime; represents times prior to that date, while a
-        positive number represents times after it.  
+        the traditional POSIX epoch.  A &ClockTime; represents a time
+         relative to midnight the morning of January 1, 1970, UTC.  A
+        negative &ClockTime; represents a number of seconds prior to that date, while a
+        positive number represents a count of seconds after it.  
hunk ./en/ch21-systems.xml 164
-            manner of handling leap seconds is system-dependant and complex,
+            manner of handling leap seconds is system-dependent and complex,
hunk ./en/ch21-systems.xml 171
-        elapsed.  You can then divide by 24 and display the elapsed time as a
+        elapsed.  You can then divide by 3600 and display the elapsed time as a
hunk ./en/ch21-systems.xml 191
-        <listitem><para id="x_ha">What will be the time on this date next
-            month?</para></listitem>
hunk ./en/ch21-systems.xml 240
-          time 1500 seconds after midnight on January 1, 1970, UTC.
+          time 1000 seconds after midnight on January 1, 1970, UTC.
+          That moment in time is known as the <emphasis>epoch</emphasis>.
hunk ./en/ch21-systems.xml 457
-      <para id="x_Ob">
+      <para>
+        The functions such as <literal>accessTime</literal> return
+        data in a POSIX-specific type called
+        <literal>EpochTime</literal>, which se convert to a
+        &ClockTime; using the <literal>toct</literal> function.
hunk ./en/ch21-systems.xml 470
-  <sect1 id="systems.cmd">
-    <title>Invoking External Commands</title>
-    <para id="x_Qb">
-      The <literal>System.Cmd</literal> module provides a cross-platform way
-      to invoke external commands.  This could let you call system utilities
-      or
-      start up programs to gather data from the user.  The functions in
-      <literal>System.Cmd</literal> pause execution of your Haskell program
-      while the new program runs, then continue where it left off after the
-      called program terminates.
-    </para>
-    <para id="x_Rb">
-      The most useful if the functions in <literal>System.Cmd</literal> is
-      <literal>rawSystem</literal>.  It takes an executble name and a list of
-      command-line arguments to pass to it, and returns an exit code.  You
-      can even test it from &ghci; like this:
-    </para>
-    &cmd.ghci:all;
-    <para id="x_Sb">
-      <literal>rawSystem</literal> does not pass the command or its arguments
-      through the shell.  This is an important safety and integrity feature.
-      The shell may perform wildcard expansion, argument parsing, and other
-      tasks on the input.  This can lead to problems or even security risks
-      when dealing with things as simple as filenames containing spaces or
-      strings containing punctuation.  For this reason, we recommend using
-      <literal>rawSystem</literal> instead of alternatives such as
-      <literal>system</literal> at all times.
-    </para>
-  </sect1>
-
hunk ./en/ch21-systems.xml 546
-        <literal>rawSystem</literal> because this would mess up the stdandard
+        <literal>rawSystem</literal> because this would mess up the standard
hunk ./examples/ch21/dir.ghci 10
-getDirectoryContents "/" >>= return . filter (\c -> not $ elem c [".", ".."])
+getDirectoryContents "/" >>= return . filter (`notElem` [".", ".."])
}