How to put variables in linux command?

Question

I want to know how to put variables in linux command, here is my code:

---

while read line
do
$site=$line
# execute extract command foreach line(each line contain a site name)
../../data/PROG/launch extractdata -hdf 2013-01-01,2014-01-01 -site  "$site"  >data/hour_$site_file.txt
 done < data/extract_site.txt

---

i explain:

this file "data/extract_site.txt" contains a list of sites name, each line is a site name, and for each site i want to extract data and put the result of the commande in a file named "hour_$site_file.txt". For example i have a site name "OPE", the command would be: ../../data/PROG/launch extractdata -hdf 2013-01-01,2014-01-01 -site OPE and the file name will be called: hour_OPE_file.txt

when i execute that i have error: undefined command "=OPE"

Iam a beginner in shell, any help?

Thanks in advance.

PS: sorry for my english, i'm french.

Answer 1

Variable name as L-value does not need $.

Variable names chained should be enclosed into brackets as in hour_${site}_file.txt

while read line
do
site=$line
# execute extract command foreach line(each line contain a site name)
../../data/PROG/launch extractdata -hdf 2013-01-01,2014-01-01 -site  "$site"  >data/hour_${site}_file.txt
 done < data/extract_site.txt

Answer 2

Use braces to separate parameter names and use quotes to prevent word splitting:

while read -r line; do
    site=$line
    ../../data/PROG/launch extractdata -hdf 2013-01-01,2014-01-01 -site "$site" > "data/hour_${site}_file.txt"
done

• When assigning a value to a variable, don't add a leading $ to the target: $site=$line was wrong.
• -r optionally prevents backslashes from input to be interpreted.