On a Linux system, we can view the Environment variables that are set and exported using 3 built-in commands:
'set', 'env' & 'export -p'.
Ever wondered how can we see the other 'unset' environment variables belongs to Bash shell or some command or tool ?
The technique that I follow is to look in 2 places: One in the Binaries of the program which the application uses and other in the MAN page.
To view all the printable strings in a Bash shell: # strings /bin/bash | grep -P '[A-Z]+'
In this output, there will be a lot of additional stuff and you will have to look for environment variables carefully
To print all the ENV variables related to 'history' command:
# man bash | sed 's/[[:cntrl:]].//g' | egrep -x ' +HIST[[:alpha:]]*'
HISTCMD
HISTCONTROL
HISTFILE
HISTFILESIZE
HISTIGNORE
HISTSIZE
HISTTIMEFORMAT
A URL that contains all the Bash variables explaining each:
