[root@localhost /]# ( ./address_to_char;cat) | ./overflow
How does ( ./address_to_char;cat) work here?
What's different from ./address_to_char|./overflow?
2 Answers
The outputs of both ./address_to_char and cat are piped to ./overflow as a single, continuous stream of data.
First,
./address_to_charis run, and its output is redirected to./overflow's input.When
./address_to_charexits,catis started, and its output is attached to the still-running./overflowprocess in the same way.Since
catwas run with no files specified, it reads from stdin (in this case, your keyboard).
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@kernel:
catexits upon reaching the end of its input. In this case, it reads from keyboard, and will exit when you press the "EOF" key (by default Ctrl-D).– user1686Apr 17, 2011 at 15:17 -
@grawity,but after testing it seems it will also exit when
./overflowexits,weird...or is that normal?– kernelApr 17, 2011 at 15:18 -
@kernel: It's normal. When the right side (
./overflow) exits, the left side doesn't have anywhere to write to, and -- AFAIK -- gets killed by signalSIGPIPE.– user1686Apr 17, 2011 at 15:23 -
@grawity,that solves most of my doubt,but still one, how can
./overflowget executed beforecatexits?– kernelApr 17, 2011 at 15:28
Well the parentheses open a sub shell and the semi colon will run the commands sequentially.
So in this case, you are running ./address_to_char then cat in a subshell.
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It seems there's no difference from
./address_to_char | ./overflow,right?– kernelApr 17, 2011 at 9:12