1run_erl(1) User Commands run_erl(1)
2
6 run_erl - Redirect Erlang input and output streams on Unix systems.
7
9 The run_erl program is specific to Unix systems. This program redirects
10 the standard input and standard output streams so that all output can
11 be logged. It also lets the program to_erl connect to the Erlang con‐
12 sole, making it possible to monitor and debug an embedded system re‐
13 motely.
14 For more information about the use, see the Embedded System User's
16 Guide in System Documentation.
17
19 run_erl [-daemon] pipe_dir/ log_dir "exec command arg1 arg2 ..."
20 Arguments:
22 -daemon:
24 This option is highly recommended. It makes run_erl run in
25 the background completely detached from any controlling ter‐
26 minal and the command returns to the caller immediately.
27 Without this option, run_erl must be started using several
28 tricks in the shell to detach it completely from the termi‐
29 nal in use when starting it. The option must be the first
30 argument to run_erl on the command line.
31 pipe_dir:
33 The named pipe, usually /tmp/. It must be suffixed by a /
34 (slash), that is, /tmp/epipes/, not /tmp/epipes.
35 log_dir:
37 The log files, that is:
38 * One log file, run_erl.log, which logs progress and warn‐
40 ings from the run_erl program itself.
41 * Up to five log files at maximum 100 KB each with the con‐
43 tent of the standard streams from and to the command.
44 (Both the number of logs and sizes can be changed by envi‐
45 ronment variables, see section Environment Variables be‐
46 low.)
47 When the logs are full, run_erl deletes and reuses the
49 oldest log file.
50 "exec command arg1 arg2 ...":
52 A space-separated string specifying the program to be exe‐
53 cuted. The second field is typically a command name such as
54 erl.
55
57 While running, run_erl sends all output, uninterpreted, to a log file.
58 The file is named erlang.log.N, where N is an integer. When the log is
59 "full" (default log size is 100 KB), run_erl starts to log in file er‐
60 lang.log.(N+1), until N reaches a certain number (default 5), whereupon
61 N starts at 1 again and the oldest files start getting overwritten.
62 If no output comes from the Erlang shell, but the Erlang machine still
64 seems to be alive, an "ALIVE" message is written to the log; it is a
65 time stamp and is written, by default, after 15 minutes of inactivity.
66 Also, if output from Erlang is logged, but more than 5 minutes (de‐
67 fault) has passed since last time we got anything from Erlang, a time
68 stamp is written in the log. The "ALIVE" messages look as follows:
69 ===== ALIVE <date-time-string>
71 The other time stamps look as follows:
73 ===== <date-time-string>
75 date-time-string is the date and time the message is written, default
77 in local time (can be changed to UTC if needed). It is formatted with
78 the ANSI-C function strftime using the format string %a %b %e %T %Z %Y,
79 which produces messages like ===== ALIVE Thu May 15 10:13:36 MEST 2003;
80 this can be changed, see the next section.
81
83 The following environment variables are recognized by run_erl and
84 change the logging behavior. For more information, see the previous
85 section.
86 RUN_ERL_LOG_ALIVE_MINUTES:
88 How long to wait for output (in minutes) before writing an "ALIVE"
89 message to the log. Defaults to 15, minimum is 1.
90 RUN_ERL_LOG_ACTIVITY_MINUTES:
92 How long Erlang needs to be inactive before output is preceded with
93 a time stamp. Defaults to RUN_ERL_LOG_ALIVE_MINUTES div 3, minimum
94 is 1.
95 RUN_ERL_LOG_ALIVE_FORMAT:
97 Specifies another format string to be used in the strftime C li‐
98 brary call. That is, specifying this to "%e-%b-%Y, %T %Z" gives log
99 messages with time stamps like 15-May-2003, 10:23:04 MET. For more
100 information, see the documentation for the C library function strf‐
101 time. Defaults to "%a %b %e %T %Z %Y".
102 RUN_ERL_LOG_ALIVE_IN_UTC:
104 If set to anything else than 0, it makes all times displayed by
105 run_erl to be in UTC (GMT, CET, MET, without Daylight Saving Time),
106 rather than in local time. This does not affect data coming from
107 Erlang, only the logs output directly by run_erl. Application SASL
108 can be modified accordingly by setting the Erlang application vari‐
109 able utc_log to true.
110 RUN_ERL_LOG_GENERATIONS:
112 Controls the number of log files written before older files are
113 reused. Defaults to 5, minimum is 2, maximum is 1000.
114 Note that, as a way to indicate the newest file, run_erl will
116 delete the oldest log file to maintain a "hole" in the file se‐
117 quences. For example, if log files #1, #2, #4 and #5 exists, that
118 means #2 is the latest and #4 is the oldest. You will therefore at
119 most get one less log file than the value set by RUN_ERL_LOG_GENER‐
120 ATIONS.
121 RUN_ERL_LOG_MAXSIZE:
123 The size, in bytes, of a log file before switching to a new log
124 file. Defaults to 100000, minimum is 1000, maximum is about 2^30.
125 RUN_ERL_DISABLE_FLOWCNTRL:
127 If defined, disables input and output flow control for the pty
128 opend by run_erl. Useful if you want to remove any risk of acciden‐
129 tally blocking the flow control by using Ctrl-S (instead of Ctrl-D
130 to detach), which can result in blocking of the entire Beam
131 process, and in the case of running heart as supervisor even the
132 heart process becomes blocked when writing log message to terminal,
133 leaving the heart process unable to do its work.
134
136 start(1), start_erl(1)
137Ericsson AB erts 13.2.2.4 run_erl(1)