12-11-2002
You can use nohup inside a script if you want to. But I think nohup was really intended to be used from the command line.
Different versions of nohup ignore different signals. Sun actually supplies two different versions. It writes to nohup.out if it can or $HOME/nohup.out if the current directory is not writable. A script that silently invokes nohup might interfer with a user's use of nohup with both writing to the same nohup.out file.
Inside a script, ignoring signals is easy. A script can in effect nohup itself by simply using:
trap "" HUP QUIT
and there is no question about whether or not QUIT is being ignored. Want to ignore TERM too? Just use:
trap "" HUP QUIT TERM
And now you can redirect the output whereever you want leaving nohup.out available for mamual use.
In my above script, you could do:
nohup date &
but
( trap "" HUP QUIT TERM ; exec date > date.out 2>&1 ) &
pretty much does the same thing, but gives me much more control over what is happening. Remember that parentheses start a subshell, so the trap inside the subshell does not affect the outer shell.
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LEARN ABOUT OPENSOLARIS
let
let(1) User Commands let(1)
NAME
let - shell built-in function to evaluate one or more arithmetic expressions
SYNOPSIS
ksh
let arg...
ksh93
let [expr...]
DESCRIPTION
ksh
Each arg is a separate arithmetic expression to be evaluated.
ksh93
let evaluates each expr in the current shell environment as an arithmetic expression using ANSI C syntax. Variables names are shell vari-
ables and they are recursively evaluated as arithmetic expressions to get numerical values. let has been made obsolete by the ((...)) syn-
tax of ksh93(1) which does not require quoting of the operators to pass them as command arguments.
EXIT STATUS
ksh
ksh returns the following exit values:
0 The value of the last expression is non-zero.
1 The value of the last expression is zero.
ksh93
ksh93 returns the following exit values:
0 The last expr evaluates to a non-zero value.
>0 The last expr evaluates to 0 or an error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO
ksh(1), ksh93(1), set(1), typeset(1), attributes(5)
SunOS 5.11 2 Nov 2007 let(1)