Question

Is it possible to create our own unix commands?
For example: we have ls -ltr,cd,mkdir etc which perform certain actions. I want to create a similar command which would save username-password into a table in database. I’m kinda new to unix. Any suggestions?

Answer 1

Yes, it is easy to create your own commands that do jobs that you find useful. You can implement them in a variety of languages, from shell to Perl to C and on and on.

The only significance to the standard commands are that they are installed (usually) in /bin or /usr/bin rather than anywhere else, and they do jobs that are defined by a standard (often POSIX). Often, people place locally created commands in /usr/local/bin; others will create themselves a directory $HOME/bin and put their personal commands there. You simply need to ensure that these directories are on your PATH.

In my $HOME/bin directory (depending on which machine I’m looking at), I have from 46 commands (on this machine) up to about 500 on my main work machines. The commands do different jobs; the names are mnemonic to me (and generally not to other people). Some commands are polished and ready for production use anywhere (and these have manual pages, almost by definition of being production-ready). Others are quick hacks assembled for a quick-and-dirty job. Some of the quick hacks are removed; some get polished; some get stashed away in case I need to do something similar in the future. Only the trivial don’t go under version control.

On this machine (which I only use casually and not really for development work), I have 9 shell scripts, 4 Perl scripts, and the rest are executables (Git and Go, mainly). On my main machines, I have many more shell and Perl scripts and proportionately fewer C programs. I have few Python scripts since I learned Perl first and I’m not as fluent in Python. I’ve been writing and collecting these scripts for a long time; the oldest versions of the oldest programs date back to about 1987.