UNIX for Dummies Questions & Answers

I've come stuck when I was making sure the hour of the day was not been two times so that the rest of the script could not be executed.
Seems simple enough.
I used the -a to join the two conditions together and it would run if the conditions was t/f ( it is only supposed to run if was t/t).
I read on this forum about using && instead of -a. It now works.
Whats the difference?

Code that doesn't work using the -a, change this to && and it works.
WORK_START_HOUR=8 # 8.00am
WORK_END_HOUR=17 # 5.00pm
CHECK_HOUR=`date +"%H"`
CHECK_HOUR=18
if [ $CHECK_HOUR -ge $WORK_START_HOUR ] -a [ $CHECK_HOUR -le $WORK_END_HOUR ]
then
echo "Hour is in the range of 8 to 17"
else
echo "Hour is in outside the range of 8 to 17"
fi


thanks
brett

You're doing two different things.

If you want to use -a, you need to use it within the test braces. You're making two tests using two sets of braces and need to use && for comparisons outside the test braces.

Code:

#!/bin/ksh

WORK_START_HOUR=8 # 8.00am
WORK_END_HOUR=17 # 5.00pm
CHECK_HOUR=`date +"%H"`
CHECK_HOUR=18
if [ $CHECK_HOUR -ge $WORK_START_HOUR ] && [ $CHECK_HOUR -le $WORK_END_HOUR ]
then
  echo "Hour is in the range of 8 to 17"
else
  echo "Hour is in outside the range of 8 to 17"
fi

Code:

#!/bin/ksh

WORK_START_HOUR=8 # 8.00am
WORK_END_HOUR=17 # 5.00pm
CHECK_HOUR=`date +"%H"`
CHECK_HOUR=18
if [ $CHECK_HOUR -ge $WORK_START_HOUR -a $CHECK_HOUR -le $WORK_END_HOUR ]
then
  echo "Hour is in the range of 8 to 17"
else
  echo "Hour is in outside the range of 8 to 17"
fi

Note the second one works because the entire test is inclosed in a single set of braces.

Carl

Great thanks
Brett

-a is used to combine 2 conditions
&& is used to combine to actions (which could be conditions)


if [ condition1 -a condition2 ] ...........

action1 && action2

e.g.
test -f /usr/bin/ls && /usr/bin/ls

First is test if the command /usr/bin/ls is present, if the test evolves to true then /usr/bin/ls is really executed.