In Linux, I know how to write a simply message to the /var/log/messages file, in a simple shell script I created:
#!/bin/bash
logger "have fun!"
I want to stop throwing messages into the default /var/log/messages file, and create my own.
I tried this:
#!/bin/bash
logger "have more fun" > /var/log/mycustomlog
It still logs to /var/log/messages. It did create the /var/log/mycustomlog, but it's empty.
Anyone see what I'm missing?
logger logs to syslog facilities. If you want the message to go to a particular file you have to modify the syslog configuration accordingly. You could add a line like this:
local7.* -/var/log/mycustomlog
and restart syslog. Then you can log like this:
logger -p local7.info "information message"
logger -p local7.err "error message"
and the messages will appear in the desired logfile with the correct log level.
Without making changes to the syslog configuration you could use logger like this:
logger -s "foo bar" 2>> /var/log/mycustomlog
Specifying -s or --stderr instructs logger to print the message to STDERR as well (in addition to logging it to syslog), so you could redirect STDERR to a file. However, it would be utterly pointless, because the message is already logged via syslog anyway (with the default priority user.notice). Note that we use here 2>> to append standard error to the file named.
- before the file path indicate? I've tried googling around but can't find anything about it. Is it required?
rsyslog.conf manual.@chepner make a good point that logger is dedicated to logging messages.
I do need to mention that @Thomas Haratyk simply inquired why I didn't simply use echo.
At the time, I didn't know about echo, as I'm learning shell-scripting, but he was right.
My simple solution is now this:
#!/bin/bash
echo "This logs to where I want, but using echo" > /var/log/mycustomlog
The example above will overwrite the file after the >
So, I can append to that file with this:
#!/bin/bash
echo "I will just append to my custom log file" >> /var/log/customlog
Thanks guys!
/var/log/, but I'm sure there are other good ideas out there. And since I didn't create a daemon, /var/log/ probably isn't the best place for my custom log file. (just saying)
/var/log is absolutely the best place for virtually any kind of log.
There's good amount of detail on logging for shell scripts via global varaibles of shell. We can emulate the similar kind of logging in shell script: http://www.cubicrace.com/2016/03/efficient-logging-mechnism-in-shell.html The post has details on introdducing log levels like INFO , DEBUG, ERROR. Tracing details like script entry, script exit, function entry, function exit.
Sample Log:
If you see the man page of logger:
$ man logger
LOGGER(1) BSD General Commands Manual LOGGER(1)
NAME logger — a shell command interface to the syslog(3) system log module
SYNOPSIS logger [-isd] [-f file] [-p pri] [-t tag] [-u socket] [message ...]
DESCRIPTION Logger makes entries in the system log. It provides a shell command interface to the syslog(3) system log module.
It Clearly says that it will log to system log. If you want to log to file, you can use ">>" to redirect to log file.
logger uses syslog or (in the case of most Linux systems) rsyslog which can be configured to place log messages where ever you like.I did it by using a filter. Most linux systems use rsyslog these days. The config files are located at /etc/rsyslog.conf and /etc/rsyslog.d.
Whenever I run the command logger -t SRI some message, I want "some message" to only show up in /var/log/sri.log.
To do this I added the file /etc/rsyslog.d/00-sri.conf with the following content.
# Filter all messages whose tag starts with SRI
# Note that 'isequal, "SRI:"' or 'isequal "SRI"' will not work.
#
:syslogtag, startswith, "SRI" /var/log/sri.log
# The stop command prevents this message from getting processed any further.
# Thus the message will not show up in /var/log/messages.
#
& stop
Then restart the rsyslogd service:
systemctl restart rsyslog.service
Here is a shell session showing the results:
[root@rpm-server html]# logger -t SRI Hello World!
[root@rpm-server html]# cat /var/log/sri.log
Jun 5 10:33:01 rpm-server SRI[11785]: Hello World!
[root@rpm-server html]#
[root@rpm-server html]# # see that nothing shows up in /var/log/messages
[root@rpm-server html]# tail -10 /var/log/messages | grep SRI
[root@rpm-server html]#
:syslogtag, startswith, consider :programname, isequal. Ref rsyslog.com/doc/v8-stable/configuration/properties.html
loggerdoesn't write to standard output; it writes to the file configured bysyslog(3)to receive log messages.