It was about three o'clock on a Thursday afternoon when Kevin called me. I remember the time because I had just been thinking about knocking off early. It had been a hard week, and the P&L was looking good, so I was ready for a break. Then my cell phone chimed, and when I pushed "Talk", Kevin's voice was in my ear.
Kevin doesn't call me all that often. We hardly ever see each other socially any more- he's in Seattle, I'm here on the East Coast. He's a Filepro and C kind of guy, neither of which I do much with any more. We keep in touch; Xmas cards and all that, but only chat now and then, and usually it's just that: chit chat.
But today Kevin had a problem. "I've got this script that keeps looping on itself and I can't figure out why".
Well, I knew better than to ask the obvious- Kevin is no fool: the script wouldn't be calling itself. But I also knew that Kevin was doing more and more Linux, so I asked "What OS?". The answer came across the country on fiber optic cables and was then broadcast for my cell phone to pick up: "Red Hat 6.1, patched to hell".
I thought for a second and said "Let's just try something- this isn't your answer, but just humor me. Put "#!/bin/sh" at the top of your script".
Kevin paused before he answered. He knows I'm not an idiot, but sometimes he wonders.. "Umm, sh is a link to bash on Linux", he said.
"I know", I explained, "but just do it anyway. Try it.". I heard keys clicking, and then his voice came back. "Son of a gun- it doesn't loop- I don't get it. What's going on?".
It was my turn to pause. "Well, I have another question, though it's really more of a statement: you have this script run when you log in, don't you?".
"That's the problem. You've done that wrong, and that's why it is looping".
Do you know what Kevin did wrong and why the "#!bin/sh" stopped the loop?
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More Articles by Tony Lawrence © 2009-11-07 Tony Lawrence
Securing a computer system has traditionally been a battle of wits: the penetrator tries to find the holes, and the designer tries to close them. (Gosser)