[SOLVED] Why does this work?

gmartin · 07-19-2009, 06:59 PM

i was just fooled by something and I need your help to understand. I have a script that runs AlienBob's script to build an install iso. My script is in /usr/local/bin. I wasn't sure of its location so I 'cd' to the directory, ran 'ls' then ran the script. Problem is that I didn't precede the script with ./ but it ran any way. My experience tells me it shouldn't have worked.

Only thing i can guess is the /usr/local/bin is in my path. Does that change the requirement for the './'

chigurh8 · 07-19-2009, 07:08 PM

Yeah, if it's in your path, ./ isn't needed.

Bruce Hill · 07-19-2009, 07:11 PM

You're in a bash shell - and it's in your $PATH, correct.

Code:

root@paul:/usr/local/sbin# mirror-slackware64-current.sh
#
# Mirroring slackware64-current from rsync.osuosl.org::slackware/slackware64-current ...
#
Changing to /backup2/ftp/pub/Linux/Slackware/slackware64-current ...
Mon Jul 20 08:08:02 CST 2009 [6553]: Getting ChangeLog.txt...
/backup2/ftp/pub/Linux/Slackware/slackware64-current
Mon Jul 20 08:08:06 CST 2009 [6553]: No difference found, exiting now....

Edit: Sorry, chigurh8, we got a lag in China ... like 50 centuries.

Nille_kungen · 07-19-2009, 07:12 PM

It work because it's in your $PATH and has the executable bit set.
'which foo.sh' should output the script if it's in your path.
The ./ only executes the script in 'pwd' and doesn't execute the script you got in your $PATH.
EDIT: i see i was to slow as well but i'm a slow typer

bgeddy · 07-19-2009, 07:43 PM

Have a look at the bash startup file /etc/profile - this is an excerpt :

Code:

# For non-root users, add the current directory to the search path:
if [ ! "`id -u`" = "0" ]; then
 PATH="$PATH:."
fi

So the current working directory gets added to the path for non root users. The file also sets the default system path here :

Code:

# Set the default system $PATH:
PATH="/usr/local/bin:/usr/bin:/bin:/usr/games"

so /usr/local/bin is set in your path anyway. If you want to check this just run :

Code:

echo $PATH

to see what the path is set too. As has been said - files in the search path will execute, (if executable), without giving their directory to the command line.

masonm · 07-19-2009, 07:43 PM

Yep, the magic word is PATH

Bruce Hill · 07-19-2009, 09:20 PM

And you don't even need the echo ... just $PATH

$PATH ... $PATH ... $PATH

gmartin · 07-19-2009, 09:39 PM

Thanks, everyone. Learned something today - and that's good!

bgeddy · 07-19-2009, 11:00 PM

Quote:

And you don't even need the echo ... just $PATH

Hmm - I always add the echo but you're quite correct - it isn't neccesary. (Just an old habit I suppose)