run_erl - Redirect Erlang input and output streams on Unix systems.
Please see following description for synopsis
run_erl(1) User Commands run_erl(1)
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 con-
sole, 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 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:
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 warn-
ings from the run_erl program itself.
* Up to five log files at maximum 100 KB each with the con-
tent of the standard streams from and to the command.
(Both the number of logs and sizes can be changed by envi-
ronment 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 exe-
cuted. 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), where-
upon N starts at 1 again and the oldest files start getting overwrit-
ten.
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 vari-
able 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.
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 acciden-
tally 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(1), start_erl(1)
Ericsson AB erts 8.3 run_erl(1)