check for all external progs like xxd inc needed version

[MaxPeal]

check for all external progs like xxd inc needed version.

e.g. on a system without xxd it don't catch the error:
root@DietPi-01:~# bash sdinfo.sh -c 1b534d454332515430615763c7013633

   ___________________  
  |                   | 
  | |               ==| 
  | |               ==| 
  | |   SDInfo      ==| 
  | |   2021-12-24  ==| 
  | |               ==| 
  | |       __    ____| 
  |________/  |__/      

sdinfo.sh: line 416: xxd: command not found
sdinfo.sh: line 422: xxd: command not found
MID : Samsung
OID :
PNM :
PRV : 30
PSN : 1633117127
MDT : 2019/6/1
AID : 956

root@DietPi-01:~#

[OneOfTheInfiniteMonkeys]

I agree, good suggestion.

It has been rather a long time since I wrote POSIX compliant scripts. Looking at the internet circa 1995, exciting!
(Repeat comment)