One of the things that excited me while learning Unix/Linux was how quickly one can perform tasks via the command line. Bash is a fully functional scripting language that incorporates Variables, Loops and If/Then statements; the bash shell allows a user to use these functions while performing adhoc tasks via the command line. This is also true for the other common shells such as bourne, korn shell, and csh.
Below I will show 5 example for loops that are run on the command line without being placed into a shell script.
Recently I was working on an issue where an application was not retaining the umask setting set in the root users profile or /etc/profile. After looking into the issue a bit it seemed that the application in question only applied the umask setting that was set in /etc/bashrc and would not even accept the values being the applications own start scripts.
After doing a bit of researched I learned a little bit more about what exactly these files do, the differences between them and when they are executed.
Today's article is going to cover a command that falls into the “I don't use this often, but when I do it's awesome” category.
The tac command is very similar to the cat command in that it is used to concatenate and print files. However there is one very large difference, the tac command does this in reverse, starting with the last line of the file and working its way up to the first line.
The cut command is a Unix/Linux tool used to literally cut text from files and output from other commands. With the cut command a user can take text and output only certain parts of the line.
In my opinion cut is the most under recognized and utilized command in Linux/Unix. This is mostly due to the fact that when most Sysadmins want to cut text from files or standard output many will reach for AWK.
For me when it comes to useful commands xargs ranks along side commands like find, top and df; xargs is a great time saver and incredibly useful. Today I will show a few examples of usage and some of the lesser known features.
Basic Usage The xargs command is used to take the output of one command and provide it as arguments to another.
# ls [0-9]-test.xml | xargs chmod -v 644 mode of `1-test.