This describes the run_erl 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 to_erl connect to the Erlang console making it
possible to monitor and debug an embedded system remotely.
You can read more about the use in the Embedded System User's Guide.
The run_erl program arguments are:
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.
This is where to put the named pipe, usually
/tmp/. It shall be suffixed by a / (slash),
i.e. not /tmp/epipies, but /tmp/epipes/.
This is where the log files are written. There will be one
log file, run_erl.log that log progress and
warnings from the run_erl 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 run_erl will delete
and reuse the oldest log file.
"exec command [command_arguments]"
In the third argument command is the to execute
where everything written to stdin and stdout is logged to
While running, run_erl (as stated earlier) sends all output,
uninterpreted, to a log file. The file is called
erlang.log.N, where N is a number. When the log is "full",
default after 100KB, run_erl starts to log in file
erlang.log.(N+1), 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:
===== ALIVE <date-time-string>
while the other timestamps look like this:
The date-time-string 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 strftime
using the format string %a %b %e %T %Z %Y, which produces
messages on the line of ===== ALIVE Thu May 15 10:13:36 MEST 2003, this can be changed, see below.
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.
How long to wait for output (in minutes) before writing an
"ALIVE" message to the log. Default is 15, can never be less
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.
Specifies another format string to be used in the strftime
C library call. i.e specifying this to "%e-%b-%Y, %T %Z"
will give log messages with timestamps looking like
15-May-2003, 10:23:04 MET etc. See the documentation
for the C library function strftime for more
information. Default is "%a %b %e %T %Z %Y".
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
sasl can be modified accordingly by setting the erlang
application variable utc_log to true.
Controls the number of log files written before older
files are being reused. Default is 5, minimum is 2, maximum is 1000.
The size (in bytes) of a log file before switching to a
new log file. Default is 100000, minimum is 1000 and maximum is