export j=0; ls *.jpg | sort -n | while read x ; do let j+=1; fn=`printf %03d $j` ; echo mv \"$x\" p$fn.jpg; done | cat renumber backwards: export j=0; ls SCN*.jpg | sort -rn | while read x ; do let j+=2; fn=`printf %03d $j` ; echo mv \"$x\" p$fn.jpg; done | cat