What does ##*/ to a env variable? How does it work?

Asked May 03 '17 at 22:00

Active May 03 '17 at 22:00

Viewed 38 times

I was reading a blog post about Docker, when the author used some kind of string manipulation to get only the last directory in a full path.

Specifically:

$ sandbox=/var/run/docker/netns/e4b8ecb7ae7c
$ echo ${sandbox##*/}
e4b8ecb7ae7c

I've tried searching for this ##/ syntax but can't find anything at all. I've also tried playing around with the ##/ to see if I can make it display other stuff, but all I can seem to do is break it.

Can someone point me to more information about this trick so that I can better understand it?

Thanks!

PS - the blog post in question if anyone is interested: http://techblog.d2-si.eu/2017/04/25/deep-dive-into-docker-overlay-networks-part-1.html

asked May 03 '17 at 22:00

otakumike

1

http://wiki.bash-hackers.org/syntax/pe – Charles Duffy May 03 '17 at 22:02
BTW, this works for *all* shell variables -- nothing specific to *environment* variables. – Charles Duffy May 03 '17 at 22:03
1

...and, specifically for the use case in this question, see the history of the relevant factoid from the irc.freenode.org #bash channel bot at http://wooledge.org/~greybot/meta/basename – Charles Duffy May 03 '17 at 22:04
Also relevant is [BashFAQ #100](http://mywiki.wooledge.org/BashFAQ/100). – Charles Duffy May 03 '17 at 22:05

What does ##*/ to a env variable? How does it work?

0 Answers0