In the tar statement

cat abc | tar xvr -

what is the real meaning for x v and f ?

thx in adv.

to find out what the switches for a certain command mean, try typing "man [name of command]"

this should give the results you are looking for.

if this fails try "info [name of command]"

this should help, but for the meantime:

for the command tar:

x - means to eXtract files from the tar

f - means to get source from named File

v - makes command Verbose, or announce all actions

-

The "-" after the "f" means the tar will
take input from the standard input (stdin).
The man page should give you detailed
information.