Dealing with repetition

Objectives

Repeat actions on multiple files using for loops and pathname expansion (AKA globbing)
Iterate on values using seq

To follow along

Please navigate to the examples/dealing_with_repetition directory

Iterating on multiple files/directories with `for` loops

Example:

for filename in data/*.dat 
do
   ./process.sh "$filename"
done

What is happening here?

data/*.dat is expanded to a list of file names via globbing or pathname expansion.
See it with echo:
```
echo data/*.dat
```
The variable filename is assigned one value from the list, for each time the loop body is executed

If the loop body is a one-liner, an alternative is particulary convenient.

Typically we use first the command to generate the list we want to iterate on.
For example:

find data -name '*.dat'

We can use a pipe and the xargs command to

find data -name '*.dat' | xargs -I{} ./process.sh {}

The for loop has also another possible syntax,

for ((i=0;i<5;i++))
do
   echo $i
done

Bash can do some arithmetic, but only with integers:

echo $((5+4))

seq can be used to generate a sequence of floating point values:

for x in `seq 0.3 0.1 1.1`
do 
    ./simulate "$x"
done