Code duplication in a shell script My bash script (lets call it `myscript`) takes input either from stdin (pipe), or form a regular file (if filename was provided as an argument) a) someprog | myscript or b) myscript file.txt Then, the data is processed line by line. At the moment, my code looks something like the following: if [ -t 0 ] ; then while read LINE do prog_1 prog_2 ... prog_n done else while read LINE do prog_1 prog_2 ... prog_n done < $1 fi This script works fine, but there seems to be too much duplicity. I am wondering whether there is a better (more elegant) way to do it. All the steps `1` to `n` are the same. The only difference is whether there is a `< $1` at the end or not. is there no better way to do it?

Functions are the general way to reduce code duplication. This case isn't any different. You just need to to define a function to implement your `while read` logic.


myfunc() {
while read LINE
do
prog_1
prog_2
...
prog_n
done
}

if [[ -t 0 ]]; then
myfunc # read stdin passed to the script
else
myfunc < "$1" # redirect file to stdin
fi