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Top Forums Shell Programming and Scripting not quite sure how to loop this script! Post 55330 by Perderabo on Thursday 9th of September 2004 06:44:49 AM
Old 09-09-2004
There is a "true" command that does nothing except set the exit code. So you could do:

while true ; do
done

to have an infinite loop. The bourne shell also has a ":" command that does nothing. It is built-in to the shell so it is faster that "true" which is external. So a second option is:

while : ; do
done

The syntax looks weird, but this is used a lot in sh scripts.
 

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true(1) 						      General Commands Manual							   true(1)

NAME
true, false - Returns a standard exit value SYNOPSIS
true false STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: true: XCU5.0 false: XCU5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. DESCRIPTION
The true command returns a 0 (zero) exit value. The false command returns a nonzero exit value. These commands are usually used in input to shell commands. NOTES
The special built-in utility : (colon) is sometimes more efficient than the true command. EXIT STATUS
[Tru64 UNIX] The nonzero value returned by the false command may vary from system to system. EXAMPLES
To construct a loop in a shell procedure, enter: while true do date sleep 60 done This procedure displays the date and time once a minute. To stop it, press the Interrupt key sequence. SEE ALSO
Commands: csh(1), ksh(1), Bourne Shell sh(1b), POSIX shell sh(1p) Standards: standards(5) true(1)
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