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run_erl

NAME

run_erl - Redirect Erlang input and output streams on Solaris®

DESCRIPTION

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.

EXPORTS

run_erl [-daemon] pipe_dir/ log_dir "exec command [command_arguments]"

The run_erl program arguments are:

-daemon

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.

pipe_dir

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/. 

log_dir

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
           log_dir.

NOTES CONCERNING THE LOG FILES

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:

 
       ===== <date-time-string>
     
 

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.

ENVIRONMENT VARIABLES

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.

RUN_ERL_LOG_ALIVE_MINUTES

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.

RUN_ERL_LOG_ACTIVITY_MINUTES

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.

RUN_ERL_LOG_ALIVE_FORMAT

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".

RUN_ERL_LOG_ALIVE_IN_UTC

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.

RUN_ERL_LOG_GENERATIONS

Controls the number of log files written before older
       files are being reused. Default is 5, minimum is 2, maximum is 1000.

RUN_ERL_LOG_MAXSIZE

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.

SEE ALSO

start_embedded(1)