bash - Create variable by combining text + another variable -

long story short, i'm trying grep value contained in first column of text file using variable.

here's sample of script, grep command doesn't work:

for ii in `cat list.txt`     grep '^$ii' >outfile.txt done 

contents of list.txt :

123,"first product",description,20.456789 456,"second product",description,30.123456 789,"third product",description,40.123456 

if perform grep '^123' list.txt, produces correct output... first line of list.txt.

if try use variable (ie grep '^ii' list.txt) "^ii command not found" error. tried combine text variable work:

var1= "'^"$ii"'" 

but var1 variable contained carriage return after $ii variable:

'^123 ' 

i've tried laundry list of things remove cr/lr (ie sed & awk), no avail. there has easier way perform grep command using variable. prefer stay grep command because works when performing manually.

you have things mixed in command grep '^ii' list.txt. character ^ beginning of line , $ value of variable. when want grep 123 in variable ii @ beginning of line, use

ii="123" grep "^$ii" list.txt 

(you should use double quotes here)
moment learning habits: continue in variable names in lowercase (well done) , use curly braces (don't harm , needed in other cases) :

ii="123" grep "^${ii}" list.txt 

now both forgetting something: our grep match 1234,"4-digit product",description,11.1111. include , in grep:

ii="123" grep "^${ii}," list.txt 

and how did "^ii command not found" error ? think used backquotes (old way nesting command, better echo "example: $(date)") , wrote

grep `^ii` list.txt # wrong !