-n option for /bin/test

[jrick]

I am trying to convert a simple script that I wrote from zsh to /bin/sh, but it seems that the behavior of the -n option for conditional tests is different from zsh.

Example from zsh:

if [[ -n `pgrep xmms2d` ]]; then
echo "This code will not be run."
fi

And in sh:

if [ -n `pgrep xmms2d` ]; then
echo "This code will run."
fi

Can anyone explain this, and a possible work around that I can use?

[DutchDaemon]

Are you looking for something like this?

if pgrep xmms2d
then
echo "This code will run."
fi

or even

pgrep xmms2d && echo "This code will run."
pgrep xmms2d || echo "This code will not run."

[jrick]

Are you looking for something like this?

if ! pgrep xmms2d

or even

pgrep xmms2d || echo "This code will run."

Well, maybe it would be good if I showed the whole script:

#!/bin/sh

UPDATE=1
SYSTEM=`uname -sr`

while :; do
DATE=`date +"%a %B %d, %I:%M %p"`
BATTERY=`sysctl -n hw.acpi.battery.life`
# if xmms2d is running
if [ -n `pgrep xmms2d` ]; then
# another if statement, stopped or not
if [ `nyxmms2 status | grep -Eo '^Stopped:'` = "Stopped:" ]; then
XMMS2=" ^fg(green)XMMS2 is stopped^fg() |"
else
XMMS2=" ^fg(green)`nyxmms2 status | grep -Eo '^[^:]+:[^:]+'`^fg() |"
fi
else
XMMS2=""
fi
echo "^fg(red)$SYSTEM^fg() |$XMMS2 ^fg(#00FFFF)$BATTERY%^fg() | ^fg(orange)$DATE^fg() "
sleep $UPDATE
done | dzen2 -fn '-*-terminus-medium-r-*-*-12-*-*-*-*-*-*-*' -bg '#222222' -fg '#aaaaaa' -w 840 -ta r -x 840

I want to test to see if xmms2d is running, and if it is, then run the rest of that code.

This almost works:

if ! pgrep xmms2d ; then
echo "test"
fi

"test" is not echoed at all, but it still prints the pid of xmms2d, which I really don't want.

[DutchDaemon]

if ! pgrep xmms2d > /dev/null 2>&1 ; then
echo "test"
fi

[jrick]

Ah yes, such a simple solution. Thanks!