Sstrhsrtj

I want to write a script to extract parts of my data file and save it in different files. I wrote a script but it gives some error. The script is

#!/bin/bash



nn=0

mn=0



for var1 in 1 2 3 ; do

    nn=nn+2

    mn=mn+302



    sed -n '$nn','$mn'p  dos.dat > $var1.dat



    nn=mn

done

The immediate problem with your script is that the variables are single-quoted, preventing them from being expanded by the shell:

sed -n '$nn','$mn'p dos.dat > $var1.dat

Perhaps you meant something like

sed -n "$nn,${mn}p" dos.dat > $var1.dat

where the second variable is delimited with { and } to separate it from p.

Also, the expression syntax is a problem. The variables on the right hand side of "=" need "$" to get their value. Without treating them with '$((' or expr, the right hand side also is just a string — not a number.

Perhaps you meant something like this:

#!/bin/bash



nn=0 ; mn=0

for var1 in 1 2 3 ; do

    nn=$(($nn+2))

    mn=$(($mn+302))



    sed -n "$nn,${mn}p" dos.dat > $var1.dat



    nn=$mn

done

According to POSIX, the '$' within $(( is unnecessary: either would work:

If the shell variable x contains a value that forms a valid integer constant, optionally including a leading plus or minus sign, then the arithmetic expansions "$((x))" and "$(($x))" shall return the same value.