WYNTK: UNIX System Admininistrator

You can run a program without its full pathname because of your command “search path.”

So how do you get from typing /bin/date on the command line to only typing date?

When you type the word date on the command line, the computer looks through the system for a command by that name. It doesn’t look everywhere. Instead, the computer searches for the command only in those directories listed in your search path. If your search path contains the directories /usr/bin, /usr/ucb, /bin, and /usr/local/bin, the computer first looks for /usr/bin/date. If it doesn’t find the date program in /usr/bin, then it looks for /usr/ucb/date. And so on, until it finds /bin/date.

Once UNIX finds a program by the name date in a directory in your search path, it executes that program.

Panic buttons

It’s happened to all of us. You run a command and then scream, “What have I done?!?”

Sometimes it’s too late. For example, if I accidentally ran the rm command when I intended to type mv..., as soon as I pressed Return, it was too late.

But often there is a way to stop a command.

Interrupt commands or mail messages with CTRL-C

When a command is still running in the foreground on the command line, you can usually stop the command by pressing CTRL-C. You know a command is still running in the foreground if you haven’t gotten your command-line prompt back yet. When you type CTRL-C, it appears on the screen as ^C.

You might want to interrupt a command because it is dangerous, or just because you don’t want to wait for it ...