Shell scripts

The following script is not an example of great programming, but shows some of the standard commands available in the UNIX shell:

l=1
for FILE in *.gif
do if test $l -ge 100
      then mv $FILE $l.gif
      elif test $l -ge 10
      then mv $FILE 0$l.gif
      else mv $FILE 00$l.gif
      fi
      l=$((l+1))
done

A standard loop can be programmed via

for (( n=1 ; n<9 ; n=$((n+1)) )); do echo $n; done