<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE comref SYSTEM "comref.dtd">
<comref>
<header>
<copyright>
<year>1999</year><year>2013</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<title>run_erl</title>
<prepared>Kent Boortz</prepared>
<responsible></responsible>
<docno></docno>
<approved></approved>
<checked></checked>
<date>99-12-15</date>
<rev></rev>
<file>run_erl.xml</file>
</header>
<com>run_erl</com>
<comsummary>Redirect Erlang input and output streams on Solaris®</comsummary>
<description>
<p>This describes the <c><![CDATA[run_erl]]></c> program specific to
Solaris/Linux. This program redirect the standard input and standard
output streams so that all output can be logged. It also let the
program <c><![CDATA[to_erl]]></c> connect to the Erlang console making it
possible to monitor and debug an embedded system remotely.</p>
<p>You can read more about the use in the <c><![CDATA[Embedded System User's Guide]]></c>.</p>
</description>
<funcs>
<func>
<name>run_erl [-daemon] pipe_dir/ log_dir "exec command [command_arguments]"</name>
<fsummary>Start the Erlang emulator without attached terminal</fsummary>
<desc>
<p>The <c><![CDATA[run_erl]]></c> program arguments are:</p>
<taglist>
<tag>-daemon</tag>
<item>This option is highly recommended. It makes run_erl run in
the background completely detached from any controlling
terminal and the command returns to the caller immediately.
Without this option, run_erl must be started using several
tricks in the shell to detach it completely from the
terminal in use when starting it. The option must be the
first argument to run_erl on the command line.</item>
<tag>pipe_dir</tag>
<item>This is where to put the named pipe, usually
<c><![CDATA[/tmp/]]></c>. It shall be suffixed by a <c><![CDATA[/]]></c> (slash),
i.e. not <c><![CDATA[/tmp/epipies]]></c>, but <c><![CDATA[/tmp/epipes/]]></c>. </item>
<tag>log_dir</tag>
<item>This is where the log files are written. There will be one
log file, <c><![CDATA[run_erl.log]]></c> that log progress and
warnings from the <c><![CDATA[run_erl]]></c> program itself and there
will be up to five log files at maximum 100KB each (both
number of logs and sizes can be
changed by environment variables, see below) with
the content of the standard streams from and to the
command. When the logs are full <c><![CDATA[run_erl]]></c> will delete
and reuse the oldest log file.</item>
<tag>"exec command [command_arguments]"</tag>
<item>In the third argument <c><![CDATA[command]]></c> is the to execute
where everything written to stdin and stdout is logged to
<c><![CDATA[log_dir]]></c>.</item>
</taglist>
</desc>
</func>
</funcs>
<section>
<title>Notes concerning the log files</title>
<p>While running, run_erl (as stated earlier) sends all output,
uninterpreted, to a log file. The file is called
<c><![CDATA[erlang.log.N]]></c>, where N is a number. When the log is "full",
default after 100KB, run_erl starts to log in file
<c><![CDATA[erlang.log.(N+1)]]></c>, until N reaches a certain number (default
5), where after N starts at 1 again and the oldest files start
getting overwritten. If no output comes from the erlang shell, but
the erlang machine still seems to be alive, an "ALIVE" message is
written to the log, it is a timestamp and is written, by default,
after 15 minutes of inactivity. Also, if output from erlang is
logged but it's been more than 5 minutes (default) since last time
we got anything from erlang, a timestamp is written in the
log. The "ALIVE" messages look like this:</p>
<code type="none"><![CDATA[
===== ALIVE <date-time-string>
]]></code>
<p>while the other timestamps look like this:</p>
<code type="none"><![CDATA[
===== <date-time-string>
]]></code>
<p>The <c><![CDATA[date-time-string]]></c> is the date and time the message is
written, default in local time (can be changed to GMT if one wants
to) and is formatted with the ANSI-C function <c><![CDATA[strftime]]></c>
using the format string <c><![CDATA[%a %b %e %T %Z %Y]]></c>, which produces
messages on the line of <c><![CDATA[===== ALIVE Thu May 15 10:13:36 MEST 2003]]></c>, this can be changed, see below.</p>
</section>
<section>
<title>Environment variables</title>
<p>The following environment variables are recognized by run_erl
and change the logging behavior. Also see the notes above to get
more info on how the log behaves.</p>
<taglist>
<tag>RUN_ERL_LOG_ALIVE_MINUTES</tag>
<item>How long to wait for output (in minutes) before writing an
"ALIVE" message to the log. Default is 15, can never be less
than 1.</item>
<tag>RUN_ERL_LOG_ACTIVITY_MINUTES</tag>
<item>How long erlang need to be inactive before output will be
preceded with a timestamp. Default is
RUN_ERL_LOG_ALIVE_MINUTES div 3, but never less than 1.</item>
<tag>RUN_ERL_LOG_ALIVE_FORMAT</tag>
<item>Specifies another format string to be used in the strftime
C library call. i.e specifying this to <c><![CDATA["%e-%b-%Y, %T %Z"]]></c>
will give log messages with timestamps looking like
<c><![CDATA[15-May-2003, 10:23:04 MET]]></c> etc. See the documentation
for the C library function strftime for more
information. Default is <c><![CDATA["%a %b %e %T %Z %Y"]]></c>.</item>
<tag>RUN_ERL_LOG_ALIVE_IN_UTC</tag>
<item>If set to anything else than "0", it will make all
times displayed by run_erl to be in UTC (GMT,CET,MET, without
DST), rather than
in local time. This does not affect data coming from erlang,
only the logs output directly by run_erl. The application
<c><![CDATA[sasl]]></c> can be modified accordingly by setting the erlang
application variable <c><![CDATA[utc_log]]></c> to <c><![CDATA[true]]></c>.</item>
<tag>RUN_ERL_LOG_GENERATIONS</tag>
<item>Controls the number of log files written before older
files are being reused. Default is 5, minimum is 2, maximum is 1000.</item>
<tag>RUN_ERL_LOG_MAXSIZE</tag>
<item>The size (in bytes) of a log file before switching to a
new log file. Default is 100000, minimum is 1000 and maximum is
approximately 2^30.</item>
<tag>RUN_ERL_DISABLE_FLOWCNTRL</tag>
<item>If defined, disables input and output flow control for the pty opend by run_erl.
Useful if you want to remove any risk of accidentally blocking the flow control
by hit Ctrl-S (instead of Ctrl-D to detach).
Which may result in blocking of the entire beam process
and in the case of running heart as supervisor
even the heart process will be blocked when writing log message to terminal.
Leaving the heart process unable to do its work.</item>
</taglist>
</section>
<section>
<title>SEE ALSO</title>
<p>start(1), start_erl(1)</p>
</section>
</comref>
