bash - How to decrement a number in each filename in a directory? -

running "ls -lrt" on terminal large list looks this:

-rw-r--r--  1 pratik  staff   1849089 jun 23 12:24 cam13-vid.webm -rw-r--r--  1 pratik  staff   1850653 jun 23 12:24 cam12-vid.webm -rw-r--r--  1 pratik  staff   1839110 jun 23 12:24 cam11-vid.webm -rw-r--r--  1 pratik  staff   1848520 jun 23 12:24 cam10-vid.webm -rw-r--r--  1 pratik  staff   1839122 jun 23 12:24 cam1-vid.webm 

i have shown part of above sample.

i rename files have number 1 less current.

for example,

mv cam1-vid.webm cam0-vid.webm mv cam2-vid.webm cam1-vid.webm ..... .... mv cam 200-vid.webm cam199-vid.webm 

how can done using os x / linux bash script (perhaps using sed) ?

you can plain bash:

for in {1..200}     mv "cam${i}-vid.webm" "cam$((i-1))-vid.webm" done