OT: awk/sed: how to use a variable in an address range?

[J65nko]

On 9/14/06, O. Hartmann <ohartman at uni-mainz.de> wrote:
[snip]
> To keep a small shell script portable I use awk for separating an ASCII
> file from a home brewn scientific model software. The datasets of the
> output is enclosed by
>
> /begin_data_set_##/
> .
> .
> .
> /end_data_set_##/
>
> ## is a two-digit counter, but not necessesaryly equidistant.
>
> I would like to separate the file contaning all datasets via awk or sed
> into appropriate files - this is my intention, but I failed.
>
> the simplest way - in theory and in my limitit ability of using sed or
> awk - is to print all lines between the (sed/awk) addresses
>
> /begin_data_set_##/
> ...
> /end_data_set_##/
>
> but this does not work due to i cannot use variables in the address
> range specifiers neither in awk nor in sed like this:
>
> awk -v nc=$NUMBER '/\/begin_data_set_nc\//,/\/end_data_set_nc\// {
> do-something-in-awk}' $input_file > $output_file_$NUMBER
>
> nc in this example is set to the counter of the desired dataset.
>
> I would like to use SED or AWK only due to portability reasons.
[snip]

You have to prefix the variable with "$" and use double quotes instead
of single quotes.
The shell will expand a variable within double quotes, but one within
single quotes

$ cat data
/start_1/
This is dataset 1
/end_1/

/start_2/
This is dataset 2
/end_2/

/start_3/
This is dataset 3
/end_3/

$ cat sed_extract

NR=$1

sed -ne "/\/start_$NR\//,/\/end_$NR\//p" data

$ sh -vx sed_extract 3

NR=$1
+ NR=3

sed -ne "/\/start_$NR\//,/\/end_$NR\//p" data
+ sed -ne /\/start_3\//,/\/end_3\//p data
/start_3/
This is dataset 3
/end_3/

$ sh -vx sed_extract 2

NR=$1
+ NR=2

sed -ne "/\/start_$NR\//,/\/end_$NR\//p" data
+ sed -ne /\/start_2\//,/\/end_2\//p data
/start_2/
This is dataset 2
/end_2/

You were close ;)