How to check if login is from localhost

yapp · 10-16-2003, 03:20 AM

yes, that is correct, the 1 isn't part of the argument list.

Code:

1> /dev/null

This redirects all output to channel 1 (standard output) to /dev/null, which is some sort of black hole device. It trashes the grep ouput, so you don't see it at the console. You may omit the "1", because it's the default.

Code:

if tty | grep "pts" 1> /dev/null; then

In this case, I pass the ouput of "tty" to "grep", ouput is trashed to /dev/null. If the "grep" exits with an exit-code indicating 'success'; ie. the pattern was found, "if" will continue with the first block.

Code:

if [ "`tty | cut -c 0-3`" -eq "tty" ]; then

# it can be re-written as:
if test "`tty | cut -c 0-3`" -eq "tty" ; then

...notice the [square blacklets] here. I forgot them
This statement is even more complex. The backticks (` ... `) are used to execute one command inside another. The result will be inserted in the orginal command line.

If you want to understand how backtick trick works, try these commands:

Code:

date
echo "Hello"
echo "Hello, it's `date` now!"

hope this helps

it's quite little technical imho, but I hope you can understand it

yapp · 10-16-2003, 03:21 AM

So your new code should be:

Code:

# Check if the word pts is found in the output of "tty":
if tty | grep "pts" 1> /dev/null; then
  echo 11
else
  echo 00
fi

# Check if the first 3 characters match "tty"
if [ "`tty | cut -c 0-3`" -eq "tty" ]; then
  echo 11
else
  echo 00
fi

this time with the square blacklets

SpecialK5106 · 10-28-2003, 10:27 PM

Sorry for not responding sooner, but I've been insanely busy. Thanks for the backtick trick, yapp! That's definitely something I'll be using now.

yapp · 10-29-2003, 07:46 AM

hi.

that doesn't matter

but thank you for dropping by.