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)