using $PATH with whereis

shanenin · 09-15-2005, 09:51 PM

I notice the whereis command does not use your $PATH variable. In particular it did not find the location of kate. So I decided to try and write an alisas that uses your $PATH variable. this code works

Code:

shane@mainbox ~ $ whereis -B {/usr,/usr/bin,/usr/kde/3.4/bin} -f kate
kate: /usr/kde/3.4/bin/kate

I would think this would also work, but it does not

Code:

shane@mainbox ~ $ whereis -B {`echo $PATH | tr ":" ","`} -f kate
kate:

what am I doing wrong

I would think the above code would expand to this, which does work

Code:

shane@mainbox ~ $ whereis -B {/bin,/usr/bin,/usr/local/bin,/opt/bin,/usr/i686-pc-linux-gnu/gcc-bin/3.3.5-20050130,/usr/i386-pc-linux-gnu/gcc-bin/3.3.5,/opt/sun-jdk-1.4.2.08/bin,/opt/sun-jdk-1.4.2.08/jre/bin,/opt/sun-jdk-1.4.2.08/jre/javaws,/usr/qt/3/bin,/usr/kde/3.4/bin,/usr/kde/3.3/bin,/usr/games/bin,/home/shane/bin} -f kate
kate: /usr/kde/3.4/bin/kate /usr/kde/3.3/bin/kate

jlliagre · 09-16-2005, 02:01 AM

try

Code:

whereis -B $(echo $PATH| tr ':' ' ')  -f kate

shanenin · 09-16-2005, 08:24 AM

thanks that works :-)

do you have an explanation why this works(using braces)

Code:

whereis -B {/usr,/usr/bin,/usr/kde/3.4/bin} -f kate

but the following methed using braces does not

Code:

shane@mainbox ~ $ whereis -B {$(echo $PATH | tr ':' ',')} -f kate
kate:

shanenin · 09-16-2005, 08:39 AM

now I understand why your method works, because items in commas and braces expand with spaces

Code:

shane@mainbox ~ $ echo {dfg,jjk}
dfg jjk

but when I do command substitution in braces it does not expand the same way

Code:

shane@mainbox ~ $ echo {$(echo dfg,ghh)}
dfg,ghh

jlliagre · 09-16-2005, 09:15 AM

Yes, this is a bash specific brace expansion feature, e.g.:

Code:

a{d,c,b}e

expands to

Code:

ade ace abe

shanenin · 09-16-2005, 09:28 AM

I wonder of the maintainers of bash left out being able to use comand subtitution in braces for a specific reason(refering to my failed code).

I also noticed this a few days ago

Code:

shane@mainbox ~ $ echo t{yh}
t{yh}

I would expect that to return tyh, but it dos not. According to bash you need at least two items seperated by commas for the properties of braces to work.