Loops in shell scripting

If you are die hard Bourne Shell (/bin/sh) scripter, it can be a challenge not to be enticed by the syntax niceties of the Born Again Borne Shell (/bin/bash).

One example is the {..} syntax

#!/bin/bash
for I in {0..5}
do
   echo $I
done

This syntax is not valid in /bin/sh on Linux.

#!/bin/sh
for I in {0..5}
do
   echo $I
done

{0..5}

NOTE: However apparently it does work in Mac OS X, which is derived from BSD, not Linux.

/bin/sh gives you a for loop but it requires the full list of iterated values instead of a range.

#!/bin/sh

for I in 0 1 2 3 4 5
do
  echo $I
done

Note: Passing a string does not work by default.

#!/bin/sh

for I in "0 1 2 3 4 5"
do
  echo $I
done

The approach to product the same result requires some format management.

#!/bin/sh

OIFS=$IFS
IFS=" "
for I in `echo "0 1 2 3 4 5"`
do
  echo $I
done
IFS=$OIFS

You can use while

#!/bin/sh

I=0
while [ $I -le 5 ]
do 
  echo $I
  I=`expr $I + 1`
done

You can use one of several other shell commands, in this example awk

#!/bin/sh

for I in `awk 'BEGIN{for (i=0;i<=5;i++) print i}'`
do 
  echo $I
done

Or, the function specifically design for sequences of numbers seq

#!/bin/sh

for I in `seq 0 5`
do 
  echo $I
done

And for these few examples, there will be more possibilities to achieve close to feature parity of the /bin/bash syntax.
An example found on BSD is jot - 0 5. This is not available Ubuntu by default but installed with the athena-jot package. However the syntax is then different for correct usage.