how to pass the parameter to command sed

linux_1 · 10-15-2007, 08:26 AM

Hello everyone.

Here I want to ask for help on "how to pass parameters to command sed"

background:
I am trying to do exercise under Csh

purpose:
just output the even line from one file.

current script:
#!/bin/csh

set Tn=`wc -l < file1`

set i = 2

while ($i <= $Tn)
sed '$i d' file1
@ i = $i + 2
end

The content of file1 is:
1
2
3
4
5
6
7
8
9
10

The problem here is that the output is always not what I want to get.
It is always as below
1
2
3
4
5
6
7
8
9
d
10

Not
2
4
6
8
10

Can you give a hand?

thank you.

marozsas · 10-15-2007, 10:31 AM

Answering exactly what you asked: Use double quotes instead....

Code:

sed "$i d" file1

Using single quotes, the sed receives the string '$i', not the expansion of $i which is 2,4,6...
Double quotes allow that expansion.

...but this will not solve your homework. try your script now and you will see the result.

pixellany · 10-15-2007, 02:00 PM

My favorite tutorial on SED:

http://www.grymoire.com/Unix/Sed.html

linux_1 · 10-15-2007, 07:10 PM

Thank you, marozsas and, Thank you, pixellany.

Your answers help me a lot. Have a nice day.