run_erl(1) User Commands run_erl(1)NAMErun_erl - Redirect Erlang input and output streams on Solaris(R)DESCRIPTION
This describes the run_erl program specific to Solaris/Linux. This pro‐
gram 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 sys‐
tem remotely.
You can read more about the use in the Embedded System User's Guide.
EXPORTSrun_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 ter‐
minal 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 termi‐
nal 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/ on Unix
or /pipe/ on OSE. 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 every‐
thing 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, uninter‐
preted, 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 modi‐
fied 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 approxi‐
mately 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 acciden‐
tally 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. Leav‐
ing the heart process unable to do its work.
SEE ALSOstart_embedded(1)Ericsson AB erts 6.3 run_erl(1)
