Changes

|{{Admon/tip|Bash Shell Scripting Tips:|<br>'''<u>Using awk to Manipulate Text</u>'''<br><br><ul><li>Very useful command for report generation, text file repair, or text and floating-point decimal manipulation. The command mimics a C program, with braces '''{ }''' that surround the action to perform based on records from a database file matching either test conditions, regular expressions, etc. Fields appear as numbers with $.<br><br></li><li>Examples:<br><br>''awk '{print}' data-file.txt''<br>''awk -F";" '{print $5,$3}' data-file.txt''<br>''awk -F"," '$4 &gt;&#61; 10000 {print $1, $2}' salary.txt''<br><br></li></ul>'''<u>Crontab (Chronograph Tables)</u>'''<br><br><ul><li>Used to automatically run (as opposed to manually run) scripts, programs, or commands. There are many tables (files), but the main one is: '''/etc/cron'''. The '''crontab''' command can be used to ''list'', ''create'', ''modify'' or ''remove'' scheduled jobs in the file.<br><br></li><li>Examples:<br><br>''crontab -e -u user'' # create/modify<br>''crontab -r -u user-name'' # remove specific user's crontab<br>''crontab -l -u username'' #List current schedules</li></ul>}}

|}

This section focuses on how to automatically run shell scripts without the Linux system administrator being there to issue that shell script. It would be highly unlikely to expect a system administrator to stay up late (eg. 2 a.m.) to manually run a shell script to terminate processes or to re-boot Linux servers. Database files (tables) are used to provide instructions on how frequent shell scripts or commands can be run.