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Full Discussion: While loops
Top Forums UNIX for Dummies Questions & Answers While loops Post 26778 by Perderabo on Friday 23rd of August 2002 09:11:17 AM
Old 08-23-2002
Personally, I dislike "while [ 1 ]" very intensely. It is an extremely misleading construct. Try this:

[ 1 ] && echo yes
[ 0 ] && echo yes

Does it really seem reasonable for both lines to do the same thing? What is happening here is that you are testing the length of a string:

[ forever ] && echo yes

would work just as well. For the test to fail, you need something like:

[ "" ] && echo yes

The colon command is shell built-in that does nothing successfully. I like to use:

while : ; do

for my infinite loops. Unix systems also have a "true" and "false" command. So

while true ; do

is another reasonable way to do infinite loops.
 

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LEARN ABOUT DEBIAN

tping

TPING(1)							   LAM COMMANDS 							  TPING(1)

NAME

       tping - Send echo messages to LAM nodes.

SYNOPSIS

       tping [-hv] [-c count] [-d delay] [-l length] nodes

OPTIONS

       -h	     Print the command help menu.

       -v	     Turn OFF verbose mode.

       -c count      Send count messages.

       -d delay      Delay delay seconds between each message.

       -l length     Each message is length bytes long.

DESCRIPTION

       The  tping  command  sends  messages  to,  and  collects replies from, a list of nodes, via the LAM echo server.  It is similar to the UNIX
       ping(8) command, and is used as a quick diagnosis of the LAM network.

       Unless options are specified, tping sends a 1 byte message an infinite number of times, displaying the roundtrip time of each message as it
       completes,  with  a delay of 1 second between roundtrips.  After the loop is broken (with keyboard interrupt, eg: ^C), tping prints statis-
       tics about all roundtrip messages.

EXAMPLES

       tping h
	   Echo messages to the local node.

       tping -v n7 -l 1000 -c 10
	   Echo 1000 byte messages to node 7.  Stay silent while working.  Stop after 10 roundtrips and report statistics.

BUGS

       There is no built-in timeout and tping will wait forever to receive an echo.  If no echo is received, due to a dead  link  or  node,  tping
       hangs.	Stop  the  process  with  a  keyboard suspend signal (eg: ^Z) and terminate LAM with lamhalt(1) or lamwipe(1) (although the use of
       lamwipe(1) is deprecated).

SEE ALSO

       lamhalt(1), lamwipe(1)

LAM 7.1.4							    July, 2007								  TPING(1)
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