Write to custom log file from a Bash script

Question

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   gt   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

User · Answer

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

User · Answer

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   gt   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   gt  gt   var log customlog   Thanks guys    on a side note  it s simply my personal preference to keep my personal logs in  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

User · Answer

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

User · Answer

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  quot information message quot  logger -p local7 err  quot error message quot   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  quot foo bar quot   gt  gt   var log mycustomlog  That would instruct 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

User · Answer

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     amp  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

[bash] Write to custom log file from a Bash script

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