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<basefont size="3"> <!--header start-->
<center><font size="2">The Open Group Base Specifications Issue 6<br>
IEEE Std 1003.1-2001<br>
Copyright &copy; 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
<!--header end-->
<hr size="2" noshade>
<h2><a name="tag_08"></a>Environment Variables</h2>
<h3><a name="tag_08_01"></a>Environment Variable Definition</h3>
<p>Environment variables defined in this chapter affect the operation of multiple utilities, functions, and applications. There are
other environment variables that are of interest only to specific utilities. Environment variables that apply to a single utility
only are defined as part of the utility description. See the ENVIRONMENT VARIABLES section of the utility descriptions in the Shell
and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001 for information on environment variable usage.</p>
<p>The value of an environment variable is a string of characters. For a C-language program, an array of strings called the
environment shall be made available when a process begins. The array is pointed to by the external variable <i>environ</i>, which
is defined as:</p>
<blockquote>
<pre>
<tt>extern char **environ;
</tt>
</pre>
</blockquote>
<p>These strings have the form <i>name</i>=<i>value</i>; <i>name</i>s shall not contain the character <tt>'='</tt> . For values to
be portable across systems conforming to IEEE&nbsp;Std&nbsp;1003.1-2001, the value shall be composed of characters from the
portable character set (except NUL and as indicated below). There is no meaning associated with the order of strings in the
environment. If more than one string in a process' environment has the same <i>name</i>, the consequences are undefined.</p>
<p>Environment variable names used by the utilities in the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001 consist
solely of uppercase letters, digits, and the <tt>'_'</tt> (underscore) from the characters defined in <a href=
"xbd_chap06.html#tagtcjh_3"><i>Portable Character Set</i></a> and do not begin with a digit. Other characters may be permitted by
an implementation; applications shall tolerate the presence of such names. Uppercase and lowercase letters shall retain their
unique identities and shall not be folded together. The name space of environment variable names containing lowercase letters is
reserved for applications. Applications can define any environment variables with names from this name space without modifying the
behavior of the standard utilities. <basefont size="2"></p>
<dl>
<dt><b>Note:</b></dt>
<dd>Other applications may have difficulty dealing with environment variable names that start with a digit. For this reason, use of
such names is not recommended anywhere.</dd>
</dl>
<basefont size="3">
<p>The <i>values</i> that the environment variables may be assigned are not restricted except that they are considered to end with
a null byte and the total space used to store the environment and the arguments to the process is limited to {ARG_MAX} bytes.</p>
<p>Other <i>name</i>= <i>value</i> pairs may be placed in the environment by, for example, calling any of the <a href=
"../functions/setenv.html"><i>setenv</i>()</a>, <a href="../functions/unsetenv.html"><i>unsetenv</i>()</a>, <sup>[<a href=
"javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> &nbsp;or <a href=
"../functions/putenv.html"><i>putenv</i>()</a> <img src="../images/opt-end.gif" alt="[Option End]" border="0"> functions,
manipulating the <i>environ</i> variable, or by using <i>envp</i> arguments when creating a process; see <i>exec</i> in the System
Interfaces volume of IEEE&nbsp;Std&nbsp;1003.1-2001.</p>
<p>It is unwise to conflict with certain variables that are frequently exported by widely used command interpreters and
applications:</p>
<center>
<table cellpadding="3" align="center">
<tr valign="top">
<td align="left">
<p class="tent"><i>ARFLAGS</i></p>
</td>
<td align="left">
<p class="tent"><i>IFS</i></p>
</td>
<td align="left">
<p class="tent"><i>MAILPATH</i></p>
</td>
<td align="left">
<p class="tent"><i>PS1</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>CC</i></p>
</td>
<td align="left">
<p class="tent"><i>LANG</i></p>
</td>
<td align="left">
<p class="tent"><i>MAILRC</i></p>
</td>
<td align="left">
<p class="tent"><i>PS2</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>CDPATH</i></p>
</td>
<td align="left">
<p class="tent"><i>LC_ALL</i></p>
</td>
<td align="left">
<p class="tent"><i>MAKEFLAGS</i></p>
</td>
<td align="left">
<p class="tent"><i>PS3</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>CFLAGS</i></p>
</td>
<td align="left">
<p class="tent"><i>LC_COLLATE</i></p>
</td>
<td align="left">
<p class="tent"><i>MAKESHELL</i></p>
</td>
<td align="left">
<p class="tent"><i>PS4</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>CHARSET</i></p>
</td>
<td align="left">
<p class="tent"><i>LC_CTYPE</i></p>
</td>
<td align="left">
<p class="tent"><i>MANPATH</i></p>
</td>
<td align="left">
<p class="tent"><i>PWD</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>COLUMNS</i></p>
</td>
<td align="left">
<p class="tent"><i>LC_MESSAGES</i></p>
</td>
<td align="left">
<p class="tent"><i>MBOX</i></p>
</td>
<td align="left">
<p class="tent"><i>RANDOM</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>DATEMSK</i></p>
</td>
<td align="left">
<p class="tent"><i>LC_MONETARY</i></p>
</td>
<td align="left">
<p class="tent"><i>MORE</i></p>
</td>
<td align="left">
<p class="tent"><i>SECONDS</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>DEAD</i></p>
</td>
<td align="left">
<p class="tent"><i>LC_NUMERIC</i></p>
</td>
<td align="left">
<p class="tent"><i>MSGVERB</i></p>
</td>
<td align="left">
<p class="tent"><i>SHELL</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>EDITOR</i></p>
</td>
<td align="left">
<p class="tent"><i>LC_TIME</i></p>
</td>
<td align="left">
<p class="tent"><i>NLSPATH</i></p>
</td>
<td align="left">
<p class="tent"><i>TERM</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>ENV</i></p>
</td>
<td align="left">
<p class="tent"><i>LDFLAGS</i></p>
</td>
<td align="left">
<p class="tent"><i>NPROC</i></p>
</td>
<td align="left">
<p class="tent"><i>TERMCAP</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>EXINIT</i></p>
</td>
<td align="left">
<p class="tent"><i>LEX</i></p>
</td>
<td align="left">
<p class="tent"><i>OLDPWD</i></p>
</td>
<td align="left">
<p class="tent"><i>TERMINFO</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>FC</i></p>
</td>
<td align="left">
<p class="tent"><i>LFLAGS</i></p>
</td>
<td align="left">
<p class="tent"><i>OPTARG</i></p>
</td>
<td align="left">
<p class="tent"><i>TMPDIR</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>FCEDIT</i></p>
</td>
<td align="left">
<p class="tent"><i>LINENO</i></p>
</td>
<td align="left">
<p class="tent"><i>OPTERR</i></p>
</td>
<td align="left">
<p class="tent"><i>TZ</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>FFLAGS</i></p>
</td>
<td align="left">
<p class="tent"><i>LINES</i></p>
</td>
<td align="left">
<p class="tent"><i>OPTIND</i></p>
</td>
<td align="left">
<p class="tent"><i>USER</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>GET</i></p>
</td>
<td align="left">
<p class="tent"><i>LISTER</i></p>
</td>
<td align="left">
<p class="tent"><i>PAGER</i></p>
</td>
<td align="left">
<p class="tent"><i>VISUAL</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>GFLAGS</i></p>
</td>
<td align="left">
<p class="tent"><i>LOGNAME</i></p>
</td>
<td align="left">
<p class="tent"><i>PATH</i></p>
</td>
<td align="left">
<p class="tent"><i>YACC</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>HISTFILE</i></p>
</td>
<td align="left">
<p class="tent"><i>LPDEST</i></p>
</td>
<td align="left">
<p class="tent"><i>PPID</i></p>
</td>
<td align="left">
<p class="tent"><i>YFLAGS</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>HISTORY</i></p>
</td>
<td align="left">
<p class="tent"><i>MAIL</i></p>
</td>
<td align="left">
<p class="tent"><i>PRINTER</i></p>
</td>
<td align="left">
<p class="tent"><i>&nbsp;</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>HISTSIZE</i></p>
</td>
<td align="left">
<p class="tent"><i>MAILCHECK</i></p>
</td>
<td align="left">
<p class="tent"><i>PROCLANG</i></p>
</td>
<td align="left">
<p class="tent"><i>&nbsp;</i></p>
</td>
</tr>
<tr valign="top">
<td align="left">
<p class="tent"><i>HOME</i></p>
</td>
<td align="left">
<p class="tent"><i>MAILER</i></p>
</td>
<td align="left">
<p class="tent"><i>PROJECTDIR</i></p>
</td>
<td align="left">
<p class="tent"><i>&nbsp;</i></p>
</td>
</tr>
</table>
</center>
<p>If the variables in the following two sections are present in the environment during the execution of an application or utility,
they shall be given the meaning described below. Some are placed into the environment by the implementation at the time the user
logs in; all can be added or changed by the user or any ancestor of the current process. The implementation adds or changes
environment variables named in IEEE&nbsp;Std&nbsp;1003.1-2001 only as specified in IEEE&nbsp;Std&nbsp;1003.1-2001. If they are
defined in the application's environment, the utilities in the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001 and the
functions in the System Interfaces volume of IEEE&nbsp;Std&nbsp;1003.1-2001 assume they have the specified meaning. Conforming
applications shall not set these environment variables to have meanings other than as described. See <a href=
"../functions/getenv.html"><i>getenv</i>()</a> and the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../utilities/xcu_chap02.html#tag_02_12">Section 2.12, Shell Execution Environment</a> for methods of accessing these
variables.</p>
<h3><a name="tag_08_02"></a>Internationalization Variables</h3>
<p>This section describes environment variables that are relevant to the operation of internationalized interfaces described in
IEEE&nbsp;Std&nbsp;1003.1-2001.</p>
<p>Users may use the following environment variables to announce specific localization requirements to applications. Applications
can retrieve this information using the <a href="../functions/setlocale.html"><i>setlocale</i>()</a> function to initialize the
correct behavior of the internationalized interfaces. The descriptions of the internationalization environment variables describe
the resulting behavior only when the application locale is initialized in this way. The use of the internationalization variables
by utilities described in the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001 is described in the ENVIRONMENT
VARIABLES section for those utilities in addition to the global effects described in this section.</p>
<dl compact>
<dt><i>LANG</i></dt>
<dd>This variable shall determine the locale category for native language, local customs, and coded character set in the absence of
the <i>LC_ALL</i> and other <i>LC_*</i> ( <i>LC_COLLATE ,</i> <i>LC_CTYPE ,</i> <i>LC_MESSAGES ,</i> <i>LC_MONETARY ,</i>
<i>LC_NUMERIC ,</i> <i>LC_TIME )</i> environment variables. This can be used by applications to determine the language to use for
error messages and instructions, collating sequences, date formats, and so on.</dd>
<dt><i>LC_ALL</i></dt>
<dd>This variable shall determine the values for all locale categories. The value of the <i>LC_ALL</i> environment variable has
precedence over any of the other environment variables starting with <i>LC_</i> ( <i>LC_COLLATE ,</i> <i>LC_CTYPE ,</i>
<i>LC_MESSAGES ,</i> <i>LC_MONETARY ,</i> <i>LC_NUMERIC ,</i> <i>LC_TIME )</i> and the <i>LANG</i> environment variable.</dd>
<dt><i>LC_COLLATE</i></dt>
<dd>This variable shall determine the locale category for character collation. It determines collation information for regular
expressions and sorting, including equivalence classes and multi-character collating elements, in various utilities and the <a
href="../functions/strcoll.html"><i>strcoll</i>()</a> and <a href="../functions/strxfrm.html"><i>strxfrm</i>()</a> functions.
Additional semantics of this variable, if any, are implementation-defined.</dd>
<dt><i>LC_CTYPE</i></dt>
<dd>This variable shall determine the locale category for character handling functions, such as <a href=
"../functions/tolower.html"><i>tolower</i>()</a>, <a href="../functions/toupper.html"><i>toupper</i>()</a>, and <a href=
"../functions/isalpha.html"><i>isalpha</i>()</a>. This environment variable determines the interpretation of sequences of bytes of
text data as characters (for example, single as opposed to multi-byte characters), the classification of characters (for example,
alpha, digit, graph), and the behavior of character classes. Additional semantics of this variable, if any, are
implementation-defined.</dd>
<dt><i>LC_MESSAGES</i></dt>
<dd>This variable shall determine the locale category for processing affirmative and negative responses and the language and
cultural conventions in which messages should be written. <sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src=
"../images/opt-start.gif" alt="[Option Start]" border="0"> &nbsp;It also affects the behavior of the <a href=
"../functions/catopen.html"><i>catopen</i>()</a> function in determining the message catalog. <img src="../images/opt-end.gif" alt=
"[Option End]" border="0"> Additional semantics of this variable, if any, are implementation-defined. The language and cultural
conventions of diagnostic and informative messages whose format is unspecified by IEEE&nbsp;Std&nbsp;1003.1-2001 should be affected
by the setting of <i>LC_MESSAGES .</i></dd>
<dt><i>LC_MONETARY</i></dt>
<dd>This variable shall determine the locale category for monetary-related numeric formatting information. Additional semantics of
this variable, if any, are implementation-defined.</dd>
<dt><i>LC_NUMERIC</i></dt>
<dd>This variable shall determine the locale category for numeric formatting (for example, thousands separator and radix character)
information in various utilities as well as the formatted I/O operations in <a href="../functions/printf.html"><i>printf</i>()</a>
and <a href="../functions/scanf.html"><i>scanf</i>()</a> and the string conversion functions in <a href=
"../functions/strtod.html"><i>strtod</i>()</a>. Additional semantics of this variable, if any, are implementation-defined.</dd>
<dt><i>LC_TIME</i></dt>
<dd>This variable shall determine the locale category for date and time formatting information. It affects the behavior of the time
functions in <a href="../functions/strftime.html"><i>strftime</i>()</a>. Additional semantics of this variable, if any, are
implementation-defined.</dd>
<dt><i>NLSPATH</i></dt>
<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
This variable shall contain a sequence of templates that the <a href="../functions/catopen.html"><i>catopen</i>()</a> function uses
when attempting to locate message catalogs. Each template consists of an optional prefix, one or more conversion specifications, a
filename, and an optional suffix.
<p>For example:</p>
<blockquote>
<pre>
<tt>NLSPATH="/system/nlslib/%N.cat"
</tt>
</pre>
</blockquote>
<p>defines that <a href="../functions/catopen.html"><i>catopen</i>()</a> should look for all message catalogs in the directory
<b>/system/nlslib</b>, where the catalog name should be constructed from the <i>name</i> parameter passed to <a href=
"../functions/catopen.html"><i>catopen</i>()</a> ( <tt>%N</tt> ), with the suffix <b>.cat</b>.</p>
<p>Conversion specifications consist of a <tt>'%'</tt> symbol, followed by a single-letter keyword. The following keywords are
currently defined:</p>
<dl compact>
<dt><tt>%N</tt></dt>
<dd>The value of the <i>name</i> parameter passed to <a href="../functions/catopen.html"><i>catopen</i>()</a>.</dd>
<dt><tt>%L</tt></dt>
<dd>The value of the <i>LC_MESSAGES</i> category.</dd>
<dt><tt>%l</tt></dt>
<dd>The <i>language</i> element from the <i>LC_MESSAGES</i> category.</dd>
<dt><tt>%t</tt></dt>
<dd>The <i>territory</i> element from the <i>LC_MESSAGES</i> category.</dd>
<dt><tt>%c</tt></dt>
<dd>The <i>codeset</i> element from the <i>LC_MESSAGES</i> category.</dd>
<dt><tt>%%</tt></dt>
<dd>A single <tt>'%'</tt> character.</dd>
</dl>
<p>An empty string is substituted if the specified value is not currently defined. The separators underscore ( <tt>'_'</tt> ) and
period ( <tt>'.'</tt> ) are not included in the <tt>%t</tt> and <tt>%c</tt> conversion specifications.</p>
<p>Templates defined in <i>NLSPATH</i> are separated by colons ( <tt>':'</tt> ). A leading or two adjacent colons <tt>"::"</tt> is
equivalent to specifying <tt>%N</tt> . For example:</p>
<blockquote>
<pre>
<tt>NLSPATH=":%N.cat:/nlslib/%L/%N.cat"
</tt>
</pre>
</blockquote>
<p>indicates to <a href="../functions/catopen.html"><i>catopen</i>()</a> that it should look for the requested message catalog in
<i>name</i>, <i>name</i><b>.cat</b>, and <b>/nlslib/</b><i>category</i><b>/</b><i>name</i><b>.cat</b>, where <i>category</i> is the
value of the <i>LC_MESSAGES</i> category of the current locale.</p>
<p>Users should not set the <i>NLSPATH</i> variable unless they have a specific reason to override the default system path. Setting
<i>NLSPATH</i> to override the default system path produces undefined results in the standard utilities and in applications with
appropriate privileges. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
</dd>
</dl>
<p>The environment variables <i>LANG ,</i> <i>LC_ALL ,</i> <i>LC_COLLATE ,</i> <i>LC_CTYPE ,</i> <i>LC_MESSAGES ,</i>
<i>LC_MONETARY ,</i> <i>LC_NUMERIC ,</i> <i>LC_TIME ,</i> <sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src=
"../images/opt-start.gif" alt="[Option Start]" border="0"> &nbsp;and <i>NLSPATH</i> <img src="../images/opt-end.gif" alt=
"[Option End]" border="0"> &nbsp;provide for the support of internationalized applications. The standard utilities shall make use
of these environment variables as described in this section and the individual ENVIRONMENT VARIABLES sections for the utilities. If
these variables specify locale categories that are not based upon the same underlying codeset, the results are unspecified.</p>
<p>The values of locale categories shall be determined by a precedence order; the first condition met below determines the
value:</p>
<ol>
<li>
<p>If the <i>LC_ALL</i> environment variable is defined and is not null, the value of <i>LC_ALL</i> shall be used.</p>
</li>
<li>
<p>If the <i>LC_*</i> environment variable ( <i>LC_COLLATE ,</i> <i>LC_CTYPE ,</i> <i>LC_MESSAGES ,</i> <i>LC_MONETARY ,</i>
<i>LC_NUMERIC ,</i> <i>LC_TIME )</i> is defined and is not null, the value of the environment variable shall be used to initialize
the category that corresponds to the environment variable.</p>
</li>
<li>
<p>If the <i>LANG</i> environment variable is defined and is not null, the value of the <i>LANG</i> environment variable shall be
used.</p>
</li>
<li>
<p>If the <i>LANG</i> environment variable is not set or is set to the empty string, the implementation-defined default locale
shall be used.</p>
</li>
</ol>
<p>If the locale value is <tt>"C"</tt> or <tt>"POSIX"</tt> , the POSIX locale shall be used and the standard utilities behave in
accordance with the rules in <a href="xbd_chap07.html#tag_07_02"><i>POSIX Locale</i></a> for the associated category.</p>
<p>If the locale value begins with a slash, it shall be interpreted as the pathname of a file that was created in the output format
used by the <a href="../utilities/localedef.html"><i>localedef</i></a> utility; see OUTPUT FILES under <a href=
"../utilities/localedef.html"><i>localedef</i></a>. Referencing such a pathname shall result in that locale being used for the
indicated category.</p>
<p><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
If the locale value has the form:</p>
<blockquote>
<pre>
<i>language</i><b>[</b><i>_territory</i><b>][</b><i>.codeset</i><b>]
</b>
</pre>
</blockquote>
<p>it refers to an implementation-provided locale, where settings of language, territory, and codeset are
implementation-defined.</p>
<p><i>LC_COLLATE ,</i> <i>LC_CTYPE ,</i> <i>LC_MESSAGES ,</i> <i>LC_MONETARY ,</i> <i>LC_NUMERIC ,</i> and <i>LC_TIME</i> are
defined to accept an additional field @ <i>modifier</i>, which allows the user to select a specific instance of localization data
within a single category (for example, for selecting the dictionary as opposed to the character ordering of data). The syntax for
these environment variables is thus defined as:</p>
<blockquote>
<pre>
<b>[</b><i>language</i><b>[</b><i>_territory</i><b>][</b><i>.codeset</i><b>][</b><tt>@</tt><i>modifier</i><b>]]
</b>
</pre>
</blockquote>
<p>For example, if a user wanted to interact with the system in French, but required to sort German text files, <i>LANG</i> and
<i>LC_COLLATE</i> could be defined as:</p>
<blockquote>
<pre>
<tt>LANG=Fr_FR
LC_COLLATE=De_DE
</tt>
</pre>
</blockquote>
<p>This could be extended to select dictionary collation (say) by use of the @ <i>modifier</i> field; for example:</p>
<blockquote>
<pre>
<tt>LC_COLLATE=De_DE@dict
</tt>
</pre>
</blockquote>
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
<p>An implementation may support other formats.</p>
<p>If the locale value is not recognized by the implementation, the behavior is unspecified.</p>
<p>At runtime, these values are bound to a program's locale by calling the <a href=
"../functions/setlocale.html"><i>setlocale</i>()</a> function.</p>
<p>Additional criteria for determining a valid locale name are implementation-defined.</p>
<h3><a name="tag_08_03"></a>Other Environment Variables</h3>
<dl compact>
<dt><i>COLUMNS</i></dt>
<dd>This variable shall represent a decimal integer &gt;0 used to indicate the user's preferred width in column positions for the
terminal screen or window; see <a href="xbd_chap03.html#tag_03_103"><i>Column Position</i></a> . If this variable is unset or null,
the implementation determines the number of columns, appropriate for the terminal or window, in an unspecified manner. When
<i>COLUMNS</i> is set, any terminal-width information implied by <i>TERM</i> is overridden. Users and conforming applications
should not set <i>COLUMNS</i> unless they wish to override the system selection and produce output unrelated to the terminal
characteristics.
<p>Users should not need to set this variable in the environment unless there is a specific reason to override the implementation's
default behavior, such as to display data in an area arbitrarily smaller than the terminal or window.</p>
</dd>
<dt><i>DATEMSK</i></dt>
<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
Indicates the pathname of the template file used by <a href="../functions/getdate.html"><i>getdate</i>()</a>. <img src=
"../images/opt-end.gif" alt="[Option End]" border="0"></dd>
<dt><i>HOME</i></dt>
<dd>The system shall initialize this variable at the time of login to be a pathname of the user's home directory. See <a href=
"pwd.h.html"><i>&lt;pwd.h&gt;</i></a> .</dd>
<dt><i>LINES</i></dt>
<dd>This variable shall represent a decimal integer &gt;0 used to indicate the user's preferred number of lines on a page or the
vertical screen or window size in lines. A line in this case is a vertical measure large enough to hold the tallest character in
the character set being displayed. If this variable is unset or null, the implementation determines the number of lines,
appropriate for the terminal or window (size, terminal baud rate, and so on), in an unspecified manner. When <i>LINES</i> is set,
any terminal-height information implied by <i>TERM</i> is overridden. Users and conforming applications should not set <i>LINES</i>
unless they wish to override the system selection and produce output unrelated to the terminal characteristics.
<p>Users should not need to set this variable in the environment unless there is a specific reason to override the implementation's
default behavior, such as to display data in an area arbitrarily smaller than the terminal or window.</p>
</dd>
<dt><i>LOGNAME</i></dt>
<dd>The system shall initialize this variable at the time of login to be the user's login name. See <a href=
"pwd.h.html"><i>&lt;pwd.h&gt;</i></a> . For a value of <i>LOGNAME</i> to be portable across implementations of
IEEE&nbsp;Std&nbsp;1003.1-2001, the value should be composed of characters from the portable filename character set.</dd>
<dt><i>MSGVERB</i></dt>
<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
Describes which message components shall be used in writing messages by <a href="../functions/fmtmsg.html"><i>fmtmsg</i>()</a>.
<img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
<dt><i>PATH</i></dt>
<dd>This variable shall represent the sequence of path prefixes that certain functions and utilities apply in searching for an
executable file known only by a filename. The prefixes shall be separated by a colon ( <tt>':'</tt> ). When a non-zero-length
prefix is applied to this filename, a slash shall be inserted between the prefix and the filename. A zero-length prefix is a legacy
feature that indicates the current working directory. It appears as two adjacent colons ( <tt>"::"</tt> ), as an initial colon
preceding the rest of the list, or as a trailing colon following the rest of the list. A strictly conforming application shall use
an actual pathname (such as <b>.</b>) to represent the current working directory in <i>PATH .</i> The list shall be searched from
beginning to end, applying the filename to each prefix, until an executable file with the specified name and appropriate execution
permissions is found. If the pathname being sought contains a slash, the search through the path prefixes shall not be performed.
If the pathname begins with a slash, the specified path is resolved (see <a href="xbd_chap04.html#tag_04_11"><i>Pathname
Resolution</i></a> ). If <i>PATH</i> is unset or is set to null, the path search is implementation-defined.</dd>
<dt><i>PWD</i></dt>
<dd>This variable shall represent an absolute pathname of the current working directory. It shall not contain any filename
components of dot or dot-dot. The value is set by the <a href="../utilities/cd.html"><i>cd</i></a> utility.</dd>
<dt><i>SHELL</i></dt>
<dd>This variable shall represent a pathname of the user's preferred command language interpreter. If this interpreter does not
conform to the Shell Command Language in the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../utilities/xcu_chap02.html">Chapter 2, Shell Command Language</a>, utilities may behave differently from those described in
IEEE&nbsp;Std&nbsp;1003.1-2001.</dd>
<dt><i>TMPDIR</i></dt>
<dd>This variable shall represent a pathname of a directory made available for programs that need a place to create temporary
files.</dd>
<dt><i>TERM</i></dt>
<dd>This variable shall represent the terminal type for which output is to be prepared. This information is used by utilities and
application programs wishing to exploit special capabilities specific to a terminal. The format and allowable values of this
environment variable are unspecified.</dd>
<dt><i>TZ</i></dt>
<dd>This variable shall represent timezone information. The contents of the environment variable named <i>TZ</i> shall be used by
the <a href="../functions/ctime.html"><i>ctime</i>()</a>, <a href="../functions/localtime.html"><i>localtime</i>()</a>, <a href=
"../functions/strftime.html"><i>strftime</i>()</a>, and <a href="../functions/mktime.html"><i>mktime</i>()</a> functions, and by
various utilities, to override the default timezone. The value of <i>TZ</i> has one of the two forms (spaces inserted for clarity):
<blockquote>
<pre>
<tt>:</tt><i>characters</i>
</pre>
</blockquote>
<p>or:</p>
<blockquote>
<pre>
<i>std offset dst offset</i><tt>,</tt> <i>rule</i>
</pre>
</blockquote>
<p>If <i>TZ</i> is of the first format (that is, if the first character is a colon), the characters following the colon are handled
in an implementation-defined manner.</p>
<p>The expanded format (for all <i>TZ s</i> whose value does not have a colon as the first character) is as follows:</p>
<blockquote>
<pre>
<i>stdoffset</i><b>[</b><i>dst</i><b>[</b><i>offset</i><b>][</b><tt>,</tt><i>start</i><b>[</b><tt>/</tt><i>time</i><b>]</b><tt>,</tt><i>end</i><b>[</b><tt>/</tt><i>time</i><b>]]]
</b>
</pre>
</blockquote>
<p>Where:</p>
<dl compact>
<dt><i>std</i>&nbsp;and&nbsp;<i>dst</i></dt>
<dd>Indicate no less than three, nor more than {TZNAME_MAX}, bytes that are the designation for the standard ( <i>std</i>) or the
alternative ( <i>dst</i> -such as Daylight Savings Time) timezone. Only <i>std</i> is required; if <i>dst</i> is missing, then the
alternative time does not apply in this locale.
<p>Each of these fields may occur in either of two formats quoted or unquoted:</p>
<ul>
<li>
<p>In the quoted form, the first character shall be the less-than ( <tt>'&lt;'</tt> ) character and the last character shall be the
greater-than ( <tt>'&gt;'</tt> ) character. All characters between these quoting characters shall be alphanumeric characters from
the portable character set in the current locale, the plus-sign ( <tt>'+'</tt> ) character, or the minus-sign ( <tt>'-'</tt> )
character. The <i>std</i> and <i>dst</i> fields in this case shall not include the quoting characters.</p>
</li>
<li>
<p>In the unquoted form, all characters in these fields shall be alphabetic characters from the portable character set in the
current locale.</p>
</li>
</ul>
<p>The interpretation of these fields is unspecified if either field is less than three bytes (except for the case when <i>dst</i>
is missing), more than {TZNAME_MAX} bytes, or if they contain characters other than those specified.</p>
</dd>
<dt><i>offset</i></dt>
<dd>Indicates the value added to the local time to arrive at Coordinated Universal Time. The <i>offset</i> has the form:
<blockquote>
<pre>
<i>hh</i><b>[</b><tt>:</tt><i>mm</i><b>[</b><tt>:</tt><i>ss</i><b>]]
</b>
</pre>
</blockquote>
<p>The minutes ( <i>mm</i>) and seconds ( <i>ss</i>) are optional. The hour ( <i>hh</i>) shall be required and may be a single
digit. The <i>offset</i> following <i>std</i> shall be required. If no <i>offset</i> follows <i>dst</i>, the alternative time is
assumed to be one hour ahead of standard time. One or more digits may be used; the value is always interpreted as a decimal number.
The hour shall be between zero and 24, and the minutes (and seconds)-if present-between zero and 59. The result of using values
outside of this range is unspecified. If preceded by a <tt>'-'</tt> , the timezone shall be east of the Prime Meridian; otherwise,
it shall be west (which may be indicated by an optional preceding <tt>'+'</tt> ).</p>
</dd>
<dt><i>rule</i></dt>
<dd>Indicates when to change to and back from the alternative time. The <i>rule</i> has the form:
<blockquote>
<pre>
<i>date</i><b>[</b><tt>/</tt><i>time</i><b>]</b><tt>,</tt><i>date</i><b>[</b><tt>/</tt><i>time</i><b>]
</b>
</pre>
</blockquote>
<p>where the first <i>date</i> describes when the change from standard to alternative time occurs and the second <i>date</i>
describes when the change back happens. Each <i>time</i> field describes when, in current local time, the change to the other time
is made.</p>
<p>The format of <i>date</i> is one of the following:</p>
<dl compact>
<dt>J<i>n</i></dt>
<dd>The Julian day <i>n</i> (1 &lt;= <i>n</i> &lt;= 365). Leap days shall not be counted. That is, in all years-including leap
years-February 28 is day 59 and March 1 is day 60. It is impossible to refer explicitly to the occasional February 29.</dd>
<dt><i>n</i></dt>
<dd>The zero-based Julian day (0 &lt;= <i>n</i> &lt;= 365). Leap days shall be counted, and it is possible to refer to February
29.</dd>
<dt>M<i>m</i>.<i>n</i>.<i>d</i></dt>
<dd>The <i>d</i>'th day (0 &lt;= <i>d</i> &lt;= 6) of week <i>n</i> of month <i>m</i> of the year (1 &lt;= <i>n</i> &lt;= 5, 1
&lt;= <i>m</i> &lt;= 12, where week 5 means &quot;the last <i>d</i> day in month <i>m</i>&quot; which may occur in either the fourth or the
fifth week). Week 1 is the first week in which the <i>d</i>'th day occurs. Day zero is Sunday.</dd>
</dl>
<p>The <i>time</i> has the same format as <i>offset</i> except that no leading sign ( <tt>'-'</tt> or <tt>'+'</tt> ) is allowed.
The default, if <i>time</i> is not given, shall be 02:00:00.</p>
</dd>
</dl>
</dd>
</dl>
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