----- Original Message ----- From: "David Bolt" <bcrafhfr@davjam.org> To: <opensuse@opensuse.org> Sent: Monday, September 29, 2008 10:02 AM Subject: Re: [opensuse] bash pipe

On Mon, 29 Sep 2008, drek wrote:-

...

Hello,

In a script I want to know in which directory I am, but I don't want to know the whole path.

This should do:

WHICHEVER_VARIABLE_NAME_YOU_WANT=${PWD##*/}

Ahh finally! Phew I was wondering if _anyone_ was going to say anything other than the unnecessary process fork of running basename. -- Brian K. White brian@aljex.com http://www.myspace.com/KEYofR +++++[>+++[>+++++>+++++++<<-]<-]>>+.>.+++++.+++++++.-.[>+<---]>++. filePro BBx Linux SCO FreeBSD #callahans Satriani Filk! -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org

On Tue, 30 Sep 2008, Randall R Schulz wrote:- <snip>

However, the second one doesn't work well if you're in "/" or a directory whose immediate parent is "/", in which case you get an empty string. The first gives you an empty string if you're in "/", which may or may not be acceptable for you. It is different than what basename and dirname yield, certainly.

True. To match the behavior of both dirname and basename, you'd need to check for an empty string and return '/' instead. Regards, David Bolt -- Team Acorn: http://www.distributed.net/ OGR-P2 @ ~100Mnodes RC5-72 @ ~15Mkeys SUSE 10.1 32 | | openSUSE 10.3 32b | openSUSE 11.0 32b | openSUSE 10.2 64b | openSUSE 10.3 64b | openSUSE 11.0 64b RISC OS 3.6 | TOS 4.02 | openSUSE 10.3 PPC | RISC OS 3.11 -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org

On Tuesday 30 September 2008 15:57, drek wrote:

On 09/29/2008 04:02 PM, David Bolt wrote:

...

This should do: WHICHEVER_VARIABLE_NAME_YOU_WANT=${PWD##*/} ^ ^ And these are curly braces.

Thanks, but... Can you explain this? For me, it is just a magic guess with some #'s and a star and slash. How do you come up with this solution?

Well, it's well-known among BASH-o-philes. It's a general mechanism for expanding a variable while simultaneously performing some pattern-directed rewriting on the expanded value (leaving the variable's value unchanged). # strips from the beginning, % from the end. A single # or % strips a minimal match (when a * is involved, other patterns or strings having a fixed length) while a double ## or %% strips a maximal match. There's also a generalized pattern editing version using (can you guess?) the slash character, '/'. Another answer to your question is: It's all in the (lengthy) BASH manual page and covered in better books on BASH scripting. I'd venture to guess that the most used case is the simple #-style prefix strip. I say this because when processing options in BASH scripts, one often has something like this: for arg; do case "$arg" in -o) optionO=1 ;; --foo=*) fooVal="${arg#--foo=}" ;; --bar=*) barVal="${arg#--bar=}" ;; -*) echo "Unknown option: \"$arg\"" >&2 eval errorCount++ ;; *) nonOptionArgs=( "${nonOptionArgs[@]}" "$arg" ) ;; esac done

André

Randall Schulz -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org

On Wed, 1 Oct 2008, drek wrote:-

On 09/29/2008 04:02 PM, David Bolt wrote:

...

This should do: WHICHEVER_VARIABLE_NAME_YOU_WANT=${PWD##*/} ^ ^ And these are curly braces. Thanks, but... Can you explain this? For me, it is just a magic guess with some #'s and a star and slash. How do you come up with this solution?

Randall has given you an explanation about what it does. As for where I came across it, initially I saw some mention of it in a book[0] I have, but didn't think much of it. Later I saw others suggesting similar constructs as solutions, so looked at the bash man page and reread that part of the book again. After doing so I've found that some of the useful, but unused by me, parameter expansions can come in handy. One of these useful expansions is this: SOME_VAR=${SOME_VAR:-value} which will assign the value "value" to SOME_VAR if it's empty, or leaves it alone if it's not. This would mean that you can get the exact same behaviour of basename by using: MY_DIR=${PWD##*/} MY_DIR=${MY_DIR:-/} or dirname using: MY_DIR=${PWD%/*} MY_DIR=${MY_DIR:-/} Just to give you a bit more insight, here's a quick comparison: davjam@adder:/local2/possible-viruses> MY_DIR="${PWD##*/}" ; MY_DIR="${MY_DIR:-/}" ; echo "${MY_DIR}" $(basename "${PWD}") possible-viruses possible-viruses davjam@adder:/local2/possible-viruses> davjam@adder:/local2/possible-viruses> MY_DIR="${PWD%/*}" ; MY_DIR="${MY_DIR:-/}" ; echo "${MY_DIR}" $(dirname "${PWD}") /local2 /local2 davjam@adder:/local2/possible-viruses> davjam@adder:/local2/possible-viruses> pushd / / /local2/possible-viruses davjam@adder:/local2/possible-viruses> davjam@adder:/> MY_DIR="${PWD##*/}" ; MY_DIR="${MY_DIR:-/}" ; echo "${MY_DIR}" $(basename "${PWD}") / / davjam@adder:/local2/possible-viruses> davjam@adder:/> MY_DIR="${PWD%/*}" ; MY_DIR="${MY_DIR:-/}" ; echo "${MY_DIR}" $(dirname "${PWD}") / / [0] Beginning Linux Programming, 3rd edition. ISBN 0-7645-4497-7 Regards, David Bolt -- Team Acorn: http://www.distributed.net/ OGR-P2 @ ~100Mnodes RC5-72 @ ~15Mkeys SUSE 10.1 32 | | openSUSE 10.3 32b | openSUSE 11.0 32b | openSUSE 10.2 64b | openSUSE 10.3 64b | openSUSE 11.0 64b RISC OS 3.6 | TOS 4.02 | openSUSE 10.3 PPC | RISC OS 3.11 -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org