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hi , I just wanna ask if it is possible to do this in UNIX: tar -xvfb 20 /dev/rct0
and if not , where is the mistake?
second what's the difference between * and $* in the begging of for when using sh?
and last what 's doing echo ${d-$1} combined with a command procedure ?
I will take a stab at the first question. You are ordering tar to extract a tar file, but what you are designating isn't one.
look into cpio
the 1st ok i did it , but what about the rest , I need some answers....
the first statement is basically a tar command used incorrectly
you are probably trying to create a backup of a tape driver /dev/rct0.
the b parameter specifies the block size which is 20 as mentioned.
x is for extract.
v is for verbose.
tar -b 20 -cvvf bkp.tar /dev/rct0
The above command would be more sensible.
The $* is used to get in the arguments.
$1 $2 etc.
Read on Shell Scripting you will understand all the, or try reading on "regular expressions" Regex
10x a lot. now if someone tell me what is doing this echo ${ d-$1 } everything will be perfect.
From man sh
And..Quote:
The syntax of the for command is:
for variable [in word ...]
do list
done
And...Quote:
$* Expands to the positional parameters, starting from one. When
the expansion occurs within a double-quoted string it expands to
a single field with the value of each parameter separated by the
first character of the IFS variable, or by a space if IFS is
unset.
rtfm?Quote:
${parameter:-word}
Use Default Values. If parameter is unset or null, the expansion
of word is substituted; otherwise, the value of parameter is sub-
stituted.
nice :) I'm so thankful for that.