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Logger In Bash



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).




Logger In Bash



I'm trying to write a simple script for MYSQL data base backup with logger function. But i'm stuck on logger, i know that it should be very simple to do, but my mind is already out. I'm using in script next string:


*If you use #!/bin/sh for your scripts, they are supposed to be posix compliant, ie run well on solaris and AIX. If ever you use some bash specific features, #!/bin/bash have to be used because there's no more portability.


When a bash command is executed it first launches the AUDIT_DEBUG(),then the trap DEBUG is disabled to avoid a useless rerun of AUDIT_DEBUG() during the execution of pipes-commands;at the end, when the prompt is displayed, it re-enables the trap DEBUG.


logger is a command-line tool used in Linux and Unix operating systems in order to add logs to the local /var/log/syslog file or remote Syslog server. logger provides different options for adding logs like setting priority, specifying a remote system or explicitly defining the Syslog port.


logger command is installed by default in most of the Linux distributions. So there is no need to install it explicitly. We can print the help and usage information with the -h option like below. The most used options of the logger command will be listed with some description.


By default, the logger command will put the given logline into the local system /var/log/syslog file. But this is not the case always. In enterprise environments, the logs should be collected and managed in a central log server. We can use the logger command in order to send the given log into the remote server by providing the IP address or hostname. We will use the -n or --server option to send the remote log server.


Linux provides a lot of tools that log their actions precisely. We can use logger command in order to send these commands output as a log. e will just use the bash shell backticks to surround command. Below we will log the command who into the syslog.


The core issue stemmed from the use of /etc/bashrc as a mechanism for enforcing command logging. The /etc/bashrc file set a read-only PROMPT_COMMAND environment variable which executed the logger command. Techniques to bypass this mechanism are detailed below. Note, this should not be considered a definitive list and further techniques to avoid the /etc/bashrc based command logging very likely exist.


Any command execution not performed via bash was not logged. For example, directly executing commands via SSH. The following figure shows a command executed via SSH and the resulting log which does not include the command:


There are many methods to log shell commands, some involve recompiling bash and others involve installing third party key logging software. Both of these options are discouraged and are risky especially on production servers.


Logging bash commands is this easy! Just logoff and log back in and all your commands will be logged in /var/log/cmdlog.log from now on. It is easily customizable what you want to log. Let me first explain how this works


The proper way to handle errors is to check if the program finished successfully or not, using return codes. It sounds obvious but return codes, an integer number stored in bash $? or $! variable, have sometimes a broader meaning. The bash man page tells you:


This bash script could potentially create a fork bomb. It has no control of how many processes to spawn at the same time, which is a big problem in a real production environment. Also, there is a limit on how many concurrent ssh sessions you can have (let alone consume bandwidth). Again, I wrote this fictional example in bash to show you how you can always improve a program to better handle errors.


Have you ever logged in to a Linux box, started running commands, and then remembered the bash history will be logging everything you run. I've done it occasionally so thought I should do some research on what the options are to hide this mistake. This is what I came up with, please get in touch if you have any other ideas.


I am trying to create a bash script and add it to my $PATH to run automatically when logging into the server. I am wanting to download FASTQC and trimgalore and add them to my bash script so they don't have to be downloaded every time I log onto the server. Does anyone know how to do this?


I'm guessing here... You have downloaded fastqc, trimgalore etc. Now you want to put them in one of the directories listed in the PATH variable so that when you login you can execute e.g. fastqc without specifying the full path to fastqc. Usually, you do this by moving the programs of interest to /bin or /.local/bin. These directories may already exist and be in $PATH, if not create them and edit /.bashrc to add them. But do echo $PATH to see first what you already have.


GenoMax I am logging into a server where I do not have root access. I am trying to download the software and make it executable through a bash script permanently. I am trying to run the programs from anywhere and not just within the FastQC/trimgalore folder.


yep. you have to call `history -a; history -r` on bash_command, because bash tries to optimize things by never reading the file, while it also tries to make it resilient to power failures by always writing the file from memory to the disk.


I did this on my mac and noticed that new terminal tabs would no longer be opened to the same working directory. To fix this, you need to not overwrite the old value of PROMPT_COMMAND. In /.bash_profile:


Instead of using echo, use a logging library such as logger or syslog-ng. These libraries allow you to log messages with different levels (e.g., info, warning, error) and provide more control over how your logs are formatted and where they are stored.


Prior to Bash 4.1 logging to syslog required either 3rd party patches, wrappers or clever hacks to glean command history information and send it to syslog. Until bash 4.1 becomes available for the majority of distributions these workaround and hacks are still useful to some who wish to obtain syslog functionality without altering, upgrading and maintaining bash manually.


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