05-14-2009
Quote:
Originally Posted by
cfajohnson
If the file is large, you shouldn't be using a shell loop.
maybe i should rephrase it. putting IFS inside the while loop(irregardless of file size), you are setting IFS every time it loops, am i right to say that? pls correct me if i am wrong.
Quote:
Putting IFS outside the loop has the disadvantage of changing it for commands inside the body of the loop as well as for the read command.
how about an example to show that... i am curious...as i seldom use the while loop like that. am i right to say , judging from your explanation, that IFS inside while loop has its own scope?
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while(n) Tcl Built-In Commands while(n)
__________________________________________________________________________________________________________________________________________________
NAME
while - Execute script repeatedly as long as a condition is met
SYNOPSIS
while test body
_________________________________________________________________
DESCRIPTION
The while command evaluates test as an expression (in the same way that expr evaluates its argument). The value of the expression must a
proper boolean value; if it is a true value then body is executed by passing it to the Tcl interpreter. Once body has been executed then
test is evaluated again, and the process repeats until eventually test evaluates to a false boolean value. Continue commands may be exe-
cuted inside body to terminate the current iteration of the loop, and break commands may be executed inside body to cause immediate termi-
nation of the while command. The while command always returns an empty string.
Note: test should almost always be enclosed in braces. If not, variable substitutions will be made before the while command starts execut-
ing, which means that variable changes made by the loop body will not be considered in the expression. This is likely to result in an
infinite loop. If test is enclosed in braces, variable substitutions are delayed until the expression is evaluated (before each loop iter-
ation), so changes in the variables will be visible. For an example, try the following script with and without the braces around $x<10:
set x 0
while {$x<10} {
puts "x is $x"
incr x
}
SEE ALSO
break(n), continue(n), for(n), foreach(n)
KEYWORDS
boolean value, loop, test, while
Tcl while(n)