Shell Programming and Scripting

Ow, if there is Solaris you'll probably want to use the utilities that are in /usr/xpg4/bin instead of the regular ones and try the script with this shell:

Code:

/usr/xpg4/bin/sh

Which is supposed to be a POSIX compliant shell as opposed to /bin/sh

If your happy with times down to the second why not use the bash SECONDS env var:

Code:

START=$SECONDS
echo Do some work here.;echo This is what we did here.
echo "Work took $((SECONDS-START)) secs"

$SECONDS also works in ksh and the Posix Shell.
It's the number of seconds since the Shell started.

I don't know about POSIX:

Code:

$ bash
$ echo $SECONDS
7
$ ksh
$ echo $SECONDS
5.652
$ dash
$ echo $SECONDS

$

@Scrutinizer
I see what you mean. ksh93 is giving time with decimal places, whereas older ksh gives whole seconds.
For consistency in a portable script we'd have to round the given figure (or just throw away the decimal places).

Code:

echo $SECONDS|cut -f1 -d'.'

The script should also test the first value of $SECONDS to make sure that the Shell has provided a value and exit if the Shell does not have the value (e.g. for original Bourne Shell) recommend that the script is run with a modern Shell.

Are there computers with just dash ? Does dash have any other useful variable?

yes, but also dash, which is a no-thrills POSIX compliant shell, does not offer $SECONDS, and I cannot find it in the POSIX specifications either. So I think it is a bash/ksh thing and not a POSIX shell thing. So I think this will maybe also not be present in /usr/xpg4/bin/sh and if it is then it should be considered an extension.


--
Sidenote: The decimal places to $SECONDS are available in ksh93, but I don't think we need to cut off the decimal places, since ksh93 can do full floating point arithmetic, so all it does is give us some extra precision, no?

Looks like another mistake in the Posix specification (even though all the Posix-compliant Shells I have do set $SECONDS).

The Posix specification lists $SECONDS as if it is a reserved variable but then does not describe the variable later on the page.
Environment Variables