How does Unix/shell scripting work? -

i curious logic of unix environment. i'm under impression unix operating system, shell. subset there more specific shells such bourne, bash, , korn shells. , these shells interpreters , have own functions interpret scripts, , have functions such ping, pwd, etc? there shells within shells? said correct?

the unix operating system not shell.

a shell program makes easy interact computer running programs , manipulating data streams.

the 'functions' mentioned programs, , not part of shell.

you can run shell shell if want. example, in bash session , want switch csh something. run csh , when you're finished, exit return bash shell.

if like, can run copy of bash inside bash session. might if want modify environment variables , undo changes when return.

in these cases, did run program shell , waited terminate. if program happened shell, it's nothing special.