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Full Discussion: cat command
Operating Systems AIX cat command Post 302453510 by Corona688 on Wednesday 15th of September 2010 01:48:32 PM
Old 09-15-2010
Quote:
Originally Posted by methyl
Both these assumptions do not stand up to benchmark testing except perhaps on the first use of "cat" after a clean boot.
Don't be ridiculous.
Code:
$ time for ((N=0; N<10000; N++)) ; do cat config | grep 32 > /dev/null ; done

real    0m21.712s
user    0m7.800s
sys     0m14.561s
$ time for ((N=0; N<10000; N++)) ; do grep 32 < config > /dev/null ; done

real    0m14.115s
user    0m5.932s
sys     0m9.381s
$

...and this is on a dual-core system. If grep had to time-share with cat, the performance would be worse yet. There is of course a cost in resources and time to launching a process and piping data through it, especially for small amounts of data. It's only insignificant when you do it once.

Last edited by Corona688; 09-15-2010 at 02:58 PM..
 

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WRITE(1)							   User Commands							  WRITE(1)

NAME
write - send a message to another user SYNOPSIS
write user [ttyname] DESCRIPTION
Write allows you to communicate with other users, by copying lines from your terminal to theirs. When you run the write command, the user you are writing to gets a message of the form: Message from yourname@yourhost on yourtty at hh:mm ... Any further lines you enter will be copied to the specified user's terminal. If the other user wants to reply, they must run write as well. When you are done, type an end-of-file or interrupt character. The other user will see the message EOF indicating that the conversation is over. You can prevent people (other than the super-user) from writing to you with the mesg(1) command. Some commands, for example nroff(1) and pr(1), may disallow writing automatically, so that your output isn't overwritten. If the user you want to write to is logged in on more than one terminal, you can specify which terminal to write to by specifying the ter- minal name as the second operand to the write command. Alternatively, you can let write select one of the terminals - it will pick the one with the shortest idle time. This is so that if the user is logged in at work and also dialed up from home, the message will go to the right place. The traditional protocol for writing to someone is that the string `-o', either at the end of a line or on a line by itself, means that it's the other person's turn to talk. The string `oo' means that the person believes the conversation to be over. SEE ALSO
mesg(1), talk(1), who(1) HISTORY
A write command appeared in Version 6 AT&T UNIX. AVAILABILITY
The write command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/. util-linux March 1995 WRITE(1)
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