passing variables to sed

jjfate · 07-29-2003, 12:22 PM

Is there a way to pass variables to sed? I would like to present a user with a list with line numbers, then prompt the user for the line number that they would like to delete. I thought that I would like to use sed to delete that line, here is what I had in mind:

cat list | more

echo "Enter line number to be deleted..."
read myNum
sed -e $myNumd

I know that I can do this to delete line 5

sed -e 5d

but I am having trouble passing variables. Any ideas? Or other solutions?

JJ

Tinkster · 07-29-2003, 05:44 PM

Something like

Code:

#!/bin/bash                                                                     
cat blah.txt | more

echo "Enter line number to be deleted..."
read myNum
cat blah.txt | sed -e "$myNum"d > blah.txt
cat blah.txt

?

Cheers,
Tink

jjfate · 07-30-2003, 01:34 PM

Tinkster,

Perfect, thank you very much it worked great!

JJ

Strike · 07-30-2003, 02:44 PM

Code:

[ddipaolo@quinn ~]% echo -e "1\n2\n3\n4\n" > temp.txt
[ddipaolo@quinn ~]% cat temp.txt
1
2
3
4

[ddipaolo@quinn ~]% export LINENUM=3
[ddipaolo@quinn ~]% sed -e `echo $LINENUM`d temp.txt
1
2
4

[ddipaolo@quinn ~]%

You get -1 point for gratuitous cat'ing to sed

Also, I'm not so sure those quotes will work for everything in general, but if it works for you great. If not, above is what I did.

Tinkster · 07-30-2003, 03:08 PM

But your solution doesn't write back to
the same file ;)

Cheers,
Tink

Strike · 07-30-2003, 10:51 PM

So redirect it to the file ...

Tinkster · 07-30-2003, 11:36 PM

Well done :)

Results in an empty file ...

Cheers,
Tink

Strike · 07-31-2003, 01:56 AM

Quote:

Originally posted by Tinkster
Well done

Results in an empty file ...

Cheers,
Tink

What?

Code:

cat temp.txt | sed -e `echo $LINENUM`d > temp.txt

If you want it to put the results in the same file, of course you'll have to use cat. But for things like piping the output of cat to more, it's just unnecessary. I was just pointing out that sed can work on files directly if you want it to.

Tinkster · 07-31-2003, 04:15 AM

Quote:

You get -1 point for gratuitous cat'ing to sed

:P

Cheers,
Tink