Cron and Crontab commands

The cron command starts a process that schedules command execution at specified dates and times.

crontab - maintain crontab files for individual users.Similar to other commands this to have options .
-u It specifies the name of the user whose crontab is to be tweaked.
-l The current crontab will be displayed on standard output.
-r The current crontab will be be removed.
-e This option is used to edit the current crontab using the editor specified by the VISUAL or EDITOR environment variables.

Usage :
#crontab -u [user_name] - e
An entry under crontab for user specified by the user_name will be made and saved automatically on exiting the editor.
#crontab -u [user_name] - l
Shows the cron jobs for the user specified.

The cron jobs deceleration needs to be done in a 5 column format consisting of
  1. minute (0-59)
  2. hour (0-23)
  3. day of the month (1-31)
  4. month of the year (1-12)
  5. day of the week (0-6 with 0=Sunday)
Taking the example that if the 'root' user desires to setup a cron job,which displayes massage "Hello Jack" on the user's [Jack] terminal at 01:45 AM everyday ,the process will go like this

#crontab -u jack - e
45 01 * * * /bin/echo "Hello Saurabh"
save and exit using ':wq' if using VI editor.

Viewing the cron job to edit
#crontab -u jack - l

Deleting the cronjob
#crontab -u jack - r

Comments

Post a Comment

Popular posts from this blog

Chrome @ Fedora

Image
Installing Chromium on Fedora isn't really all that much harder than it is on a Debian-based system. But with Fedora you have a couple of different options. You can either install from command line or you can install using the yum package management too. The benefit of installing via yum is that you will be able to update Either way the installation is simple. Let's take a look at the Yum. You have to follow the following steps: Open your vi editor and enter the gain 'root' access. Create the '/etc/yum.repos.d/chromium.repo' file. Add the following contents to the file: [chromium] name=Chromium Test Packages baseurl=http://spot.fedorapeople.org/chromium/F11/ enabled=1 gpgcheck=0 Save the file. Update the yum database using : 'yum update' Finally fire the install : 'yum install chromium -y' Doing this all will install Chromium on your fedora 11 system.Which can be accessed from under Applications -> Internet -> Chromium Web Browser The
Read more

Bash Scripting Cookies

- Passing arguments to a Bash script. `basename $0` in the script will list the name of the script without the path. `dirname $0` in the script will list the absolute path of the script without the name. `$0` will list the full path 'URI' of the script. `$#` will list the count of the arguments passed to the script. `$*` will be listing all the arguments passed to the script. `$1` will be listing the first argument passed to the script. - If conditional statements Condition Meaning [ -a FILE ] True if FILE exists. [ -b FILE ] True if FILE exists and is a block-special file. [ -c FILE ] True if FILE exists and is a character-special file. [ -d FILE ] True if FILE exists and is a directory. [ -e FILE ] True if FILE exists. [ -f FILE ] True if FILE exists and is a regular file. [ -g FILE ] True if FILE exists and its SGID bit is set. [ -h FILE ] True if FILE exists and is a symbolic link. [ -k FILE ] True if FILE exists and its sticky bit is s
Read more

Dock the Appications

Image
The day can be called successful one again as found a application that works with any kind of window managers having being tested with Gnome, KDE, XFCE as mentioned by the developer/s. So considered to give a try. 1. Installation was quick as its just a 95k package. # yum install -y kdocker.i586 2. Using it to Dock. The Docker application was found under Applications > Accessories > KDocker. Selecting the Docker turned my pointer into a kind of stock gun target. Decided to dock thunderbird, hence clicked the mouse on the application window, and it was done. 3. The icon looked a little bad but considering the work done can be acceptable.Here is the screen shot of how the docked thunderbird looked like. 4. Once docked the application can be undocked  by a single click on the docked icon of the application. 5. As seen in the above screen shot there is a terminal also docked along with the thunderbird. Great thanks to the development team.A small info about the appl
Read more