From 965db6494f80e4c784aa3bb1cd96dd925ce8b284 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn-Egil=20Dahlberg?= <egil@erlang.org>
Date: Wed, 7 Dec 2011 23:37:11 +0100
Subject: Document file:*_file_info/2

  * file:read_file_info/2
  * file:write_file_info/3

Document options and time behavior.
---
 lib/kernel/doc/src/file.xml | 52 ++++++++++++++++++++++++++++++++++-----------
 lib/kernel/src/file.erl     | 10 ++++++---
 2 files changed, 47 insertions(+), 15 deletions(-)

diff --git a/lib/kernel/doc/src/file.xml b/lib/kernel/doc/src/file.xml
index c6a1f25dd9..b2e6962be8 100644
--- a/lib/kernel/doc/src/file.xml
+++ b/lib/kernel/doc/src/file.xml
@@ -149,6 +149,9 @@
     <datatype>
       <name name="mode"/>
     </datatype>
+    <datatype>
+      <name name="file_info_option"/>
+    </datatype>
     <datatype>
       <name name="sendfile_option"/>
     </datatype>
@@ -412,7 +415,7 @@
       <name>file_info(Filename) -> {ok, FileInfo} | {error, Reason}</name>
       <fsummary>Get information about a file (deprecated)</fsummary>
       <desc>
-        <p>This function is obsolete. Use <c>read_file_info/1</c>
+        <p>This function is obsolete. Use <c>read_file_info/1,2</c>
           instead.</p>
       </desc>
     </func>
@@ -1188,6 +1191,7 @@
     </func>
     <func>
       <name name="read_file_info" arity="1"/>
+      <name name="read_file_info" arity="2"/>
       <fsummary>Get information about a file</fsummary>
       <desc>
         <p>Retrieves information about a file. Returns
@@ -1199,6 +1203,20 @@
           from which the function is called:</p>
         <code type="none">
 -include_lib("kernel/include/file.hrl").</code>
+		<p>The time type returned in <c>atime</c>, <c>mtime</c> and <c>ctime</c>
+			is dependent on the time type set in <c>Opts :: {time, Type}</c>.
+			Type <c>local</c> will return local time, <c>universal</c> will
+			return universal time and <c>posix</c> will return seconds since
+			or before unix time epoch which is 1970-01-01 00:00 UTC. 
+			Default is <c>{time, local}</c>.
+		</p> 
+		<note>
+          <p>
+			  Since file times is stored in posix time on most OS it is
+			  faster to query file information with the <c>posix</c> option.
+		  </p> 
+        </note>
+        
         <p>The record <c>file_info</c> contains the following fields.</p>
         <taglist>
           <tag><c>size = integer()</c></tag>
@@ -1213,15 +1231,15 @@
           <item>
             <p>The current system access to the file.</p>
           </item>
-          <tag><c>atime = <seealso marker="#type-date_time">date_time()</seealso></c></tag>
+          <tag><c>atime = <seealso marker="#type-date_time">date_time()</seealso> | integer() </c></tag> 
           <item>
-            <p>The last (local) time the file was read.</p>
+            <p>The last time the file was read.</p>
           </item>
-          <tag><c>mtime = <seealso marker="#type-date_time">date_time()</seealso></c></tag>
+          <tag><c>mtime = <seealso marker="#type-date_time">date_time()</seealso> | integer() </c></tag> 
           <item>
-            <p>The last (local) time the file was written.</p>
+            <p>The last time the file was written.</p>
           </item>
-          <tag><c>ctime = <seealso marker="#type-date_time">date_time()</seealso></c></tag>
+          <tag><c>ctime = <seealso marker="#type-date_time">date_time()</seealso> | integer() </c></tag> 
           <item>
             <p>The interpretation of this time field depends on
               the operating system. On Unix, it is the last time
@@ -1377,9 +1395,11 @@
     </func>
     <func>
       <name name="read_link_info" arity="1"/>
+      <name name="read_link_info" arity="2"/>
       <fsummary>Get information about a link or file</fsummary>
       <desc>
-        <p>This function works like <c>read_file_info/1</c>, except that
+		  <p>This function works like 
+			 <seealso marker="#read_file_info/2">read_file_info/1,2</seealso> except that
           if <c><anno>Name</anno></c> is a symbolic link, information about
           the link will be returned in the <c>file_info</c> record and
           the <c>type</c> field of the record will be set to
@@ -1690,6 +1710,7 @@
     </func>
     <func>
       <name name="write_file_info" arity="2"/>
+      <name name="write_file_info" arity="3"/>
       <fsummary>Change information about a file</fsummary>
       <desc>
         <p>Change file information. Returns <c>ok</c> if successful,
@@ -1700,18 +1721,25 @@
           from which the function is called:</p>
         <code type="none">
 -include_lib("kernel/include/file.hrl").</code>
+		<p>The time type set in <c>atime</c>, <c>mtime</c> and <c>ctime</c>
+			is dependent on the time type set in <c>Opts :: {time, Type}</c>.
+			Type <c>local</c> will interpret the time set as local, <c>universal</c> will
+			interpret it as universal time and <c>posix</c> must be seconds since
+			or before unix time epoch which is 1970-01-01 00:00 UTC.
+			Default is <c>{time, local}</c>.
+		</p>
         <p>The following fields are used from the record, if they are
           given.</p>
         <taglist>
-          <tag><c>atime = <seealso marker="#type-date_time">date_time()</seealso></c></tag>
+          <tag><c>atime = <seealso marker="#type-date_time">date_time()</seealso> | integer()</c></tag>
           <item>
-            <p>The last (local) time the file was read.</p>
+            <p>The last time the file was read.</p>
           </item>
-          <tag><c>mtime = <seealso marker="#type-date_time">date_time()</seealso></c></tag>
+          <tag><c>mtime = <seealso marker="#type-date_time">date_time()</seealso> | integer()</c></tag>
           <item>
-            <p>The last (local) time the file was written.</p>
+            <p>The last time the file was written.</p>
           </item>
-          <tag><c>ctime = <seealso marker="#type-date_time">date_time()</seealso></c></tag>
+          <tag><c>ctime = <seealso marker="#type-date_time">date_time()</seealso> | integer()</c></tag>
           <item>
             <p>On Unix, any value give for this field will be ignored
               (the "ctime" for the file will be set to the current
diff --git a/lib/kernel/src/file.erl b/lib/kernel/src/file.erl
index 7a48d34a09..b253b3e901 100644
--- a/lib/kernel/src/file.erl
+++ b/lib/kernel/src/file.erl
@@ -109,6 +109,10 @@
 -type posix_file_advise() :: 'normal' | 'sequential' | 'random'
                            | 'no_reuse' | 'will_need' | 'dont_need'.
 -type sendfile_option() :: {chunk_size, non_neg_integer()}.
+-type file_info_option() :: {'time', 'local'} | {'time', 'universal'} 
+			  | {'time', 'posix'}.
+
+
 %%%-----------------------------------------------------------------
 %%% General functions
 
@@ -218,7 +222,7 @@ read_file_info(Name) ->
 
 -spec read_file_info(Filename, Opts) -> {ok, FileInfo} | {error, Reason} when
       Filename :: name(),
-      Opts :: list(),
+      Opts :: [file_info_option()],
       FileInfo :: file_info(),
       Reason :: posix() | badarg.
 
@@ -240,7 +244,7 @@ read_link_info(Name) ->
 
 -spec read_link_info(Name, Opts) -> {ok, FileInfo} | {error, Reason} when
       Name :: name(),
-      Opts :: list(),
+      Opts :: [file_info_option()],
       FileInfo :: file_info(),
       Reason :: posix() | badarg.
 
@@ -266,7 +270,7 @@ write_file_info(Name, Info = #file_info{}) ->
 
 -spec write_file_info(Filename, FileInfo, Opts) -> ok | {error, Reason} when
       Filename :: name(),
-      Opts :: list(),
+      Opts :: [file_info_option()],
       FileInfo :: file_info(),
       Reason :: posix() | badarg.
 
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