sed with pathnames

rose_bud4201 · 05-22-2005, 04:12 PM

'allo all. Quick question - how do you replace the "." in a ls -lRa directory name with the actual current pwd?

When I try

Code:

[me@localhost ~/temp]$ working_dir='./'
[me@localhost ~/temp]$ echo $working_dir
./
[me@localhost ~/temp]$ pwd=`pwd`
[me@localhost ~/temp]$ echo $pwd
/home/me/temp
[me@localhost ~/temp]$ working_dir=`echo $working_dir | sed -e s/./$pwd/g`
sed: -e expression #1, char 6: Unknown option to `s'
[me@localhost ~/temp]$ working_dir=`echo $working_dir | sed -e s/./\/home\/me\/temp/g`
sed: -e expression #1, char 6: Unknown option to `s'

The first time I tried just using the variable containing an unescaped pathname, the 2nd time I tried excaping the /'s in the pathname. Both times, though, I get the same error message.

Can someone shed some light on this?

keefaz · 05-22-2005, 04:21 PM

Try :

Code:

sed -e 's/^\.//'

Edit : err... I am not sure I get it well, sorry

rose_bud4201 · 05-22-2005, 04:31 PM

Hmm, and that works...just not far enough. I realize that I gave a bad example when I first posted, though.
Given a directory /home/me/temp/subdir, that has a couple of files in it;
And given a subdirectory listing, such as would be returned from ls -Ra:

./subdir:
file1
file2

I want to get the fully-qualified pathname of file1 and file2. So what I figure I could do is take "./subdir:", get rid of the ":" with

Code:

for i in `ls -Ra`; do
    if [[ "$i" == *: ]]; then
        dirname=`echo $i | sed -e s/://g`

and then replace the "./" with the real pathname, which is /home/me/temp, giving me
/home/me/temp/subidir..which I could then concatenate onto 'file1' and 'file2' when I needed them.

Is there any way to do this?

druuna · 05-22-2005, 04:38 PM

The problem with your first example is the content of the pwd command: It holds forward slashes, this will confuse sed (forward slash being the normal seperator).

Change the seperator and you'll be ok. Also, the . and g can go. The searchstring should be \.

echo $working_dir | sed -e s%\.%$pwd%

Hope this helps.

rose_bud4201 · 05-22-2005, 04:50 PM

Oh, wow - that's really a neat trick! I never fail to learn something here

Many thanks keefaz and druuna!

eddiebaby1023 · 05-23-2005, 05:01 PM

You might also like to get the current working directory with /bin/pwd instead of the shell builtin so you get the real path, unwound of symlinks.

BTW, you can use pretty much any punctuation character as the separator, so you can tailor the sed command appropriately to minimise the amount of character escaping you have to do.

rose_bud4201 · 05-23-2005, 05:25 PM

Yeah, the problem with using just pwd is that I need to get the full path of a directory that I'm not actually in, so it had to be 'pwd' + 'relative path of the directory I'm interested in minus the ./ and ending /'

And using sed like that is quite nifty, I'm glad to know of it!

eddiebaby1023 · 05-24-2005, 08:03 AM

Quote:

Originally posted by rose_bud4201
Yeah, the problem with using just pwd is that I need to get the full path of a directory that I'm not actually in, so it had to be 'pwd' + 'relative path of the directory I'm interested in minus the ./ and ending /'

No, you misunderstood what I was saying about "pwd". The shell builtin will show you path you used to get to your current directory, /bin/pwd will show you the real path to it. To demonstrate, "cd /tmp; ln -s /tmp tempo; cd tempo". Then run "pwd", and "/bin/pwd" and spot the difference.

rose_bud4201 · 05-24-2005, 09:09 AM

hmm, interesting. I figured out how to solve the problem awhile ago, but this is worth remembering. I'm constantly up against this at work, where I've got directory symlinks all over the freakin' place

eddiebaby1023 · 05-25-2005, 07:44 AM

In a C program, you can use realpath(3). The pwd-/bin/pwd differences can be a bit confusing the first time you come across it!