NAME

       run_erl - Redirect Erlang input and output streams on Unix systems.

DESCRIPTION

       The  run_erl  program is specific to Unix systems. This program redirects the standard input and standard
       output streams so that all output can be logged. It also lets the program to_erl connect  to  the  Erlang
       console, making it possible to monitor and debug an embedded system remotely.

       For more information about the use, see the  Embedded System User's Guide in System Documentation.

EXPORTS

       run_erl [-daemon] pipe_dir/ log_dir "exec command arg1 arg2 ..."

              Arguments:

                -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:
                  The  named pipe, usually /tmp/. It must be suffixed by a / (slash), that is, /tmp/epipes/, not
                  /tmp/epipes.

                log_dir:
                  The log files, that is:

                  * One log file, run_erl.log, which logs progress and warnings from the run_erl program itself.

                  * Up to five log files at maximum 100 KB each with the content of the  standard  streams  from
                    and  to  the  command.  (Both  the  number  of  logs and sizes can be changed by environment
                    variables, see section Environment Variables below.)

                    When the logs are full, run_erl deletes and reuses the oldest log file.

                "exec command arg1 arg2 ...":
                  A space-separated string specifying the program to be executed. The second field is  typically
                  a command name such as erl.

NOTES CONCERNING THE LOG FILES

       While  running,  run_erl  sends all output, uninterpreted, to a log file. The file is named erlang.log.N,
       where N is an integer. When the log is "full" (default log size is 100 KB), run_erl starts to log in file
       erlang.log.(N+1),  until  N  reaches  a certain number (default 5), whereupon 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 time stamp and is written, by default, after 15 minutes of
       inactivity. Also, if output from Erlang is logged, but more than 5 minutes  (default)  has  passed  since
       last  time  we got anything from Erlang, a time stamp is written in the log. The "ALIVE" messages look as
       follows:

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

       The other time stamps look as follows:

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

       date-time-string is the date and time the message is written, default in local time (can  be  changed  to
       UTC  if needed). It is formatted with the ANSI-C function strftime using the format string %a %b %e %T %Z
       %Y, which produces messages like ===== ALIVE Thu May 15 10:13:36 MEST 2003; this can be changed, see  the
       next section.

ENVIRONMENT VARIABLES

       The  following  environment variables are recognized by run_erl and change the logging behavior. For more
       information, see the previous section.

         RUN_ERL_LOG_ALIVE_MINUTES:
           How long to wait for output (in minutes) before writing an "ALIVE" message to the  log.  Defaults  to
           15, minimum is 1.

         RUN_ERL_LOG_ACTIVITY_MINUTES:
           How  long  Erlang  needs  to  be  inactive  before  output is preceded with a time stamp. Defaults to
           RUN_ERL_LOG_ALIVE_MINUTES div 3, minimum is 1.

         RUN_ERL_LOG_ALIVE_FORMAT:
           Specifies another format string to be used in the strftime C library call. That is,  specifying  this
           to  "%e-%b-%Y,  %T  %Z"  gives log messages with time stamps like 15-May-2003, 10:23:04 MET. For more
           information, see the documentation for the C library function strftime. Defaults to "%a %b %e  %T  %Z
           %Y".

         RUN_ERL_LOG_ALIVE_IN_UTC:
           If  set to anything else than 0, it makes all times displayed by run_erl to be in UTC (GMT, CET, MET,
           without Daylight Saving Time), rather than in local time. This  does  not  affect  data  coming  from
           Erlang,  only  the  logs  output directly by run_erl. 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 reused. Defaults to 5, minimum is  2,
           maximum is 1000.

           Note  that, as a way to indicate the newest file, run_erl will delete the oldest log file to maintain
           a "hole" in the file sequences. For example, if log files #1, #2, #4 and #5 exists, that means #2  is
           the  latest and #4 is the oldest. You will therefore at most get one less log file than the value set
           by RUN_ERL_LOG_GENERATIONS.

         RUN_ERL_LOG_MAXSIZE:
           The size, in bytes, of a log file before switching to a new log file. Defaults to 100000, minimum  is
           1000, maximum is about 2^30.

         RUN_ERL_DISABLE_FLOWCNTRL:
           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 using Ctrl-S (instead  of  Ctrl-D  to
           detach), which can result in blocking of the entire Beam process, and in the case of running heart as
           supervisor even the heart process becomes blocked when writing log message to terminal,  leaving  the
           heart process unable to do its work.

SEE ALSO

       start_embedded(1), start_erl(1)