arithmetic syntax error in shell script

Question

There is a tool in Shell Script which Displays the menu in center and do some task.I get this error while running the script :

\007
In center function
COLUMNS : columns 142
2 : 13
/ShellsAndSQLs/task_menu: line 80:  (columns 142 - 13) / 2 : arithmetic syntax error

This code was copied from solaris env where echo $COLUMNS(why??) show blank value.This when copied to Redhat Env shows echo $COLUMNS as 142(as it should in full screen).Here is the relevent section of the code :

#!/bin/ksh 

trap "tput sgr0; tput clear;" 1 2 3 4 5 6 7 8 10 11 12 13 14 15

if [ $# -ne 2 ]
then
    echo "Wrong parameters specified" >&2
    exit 1
fi

if [ "$COLUMNS" = "" ]
then
    echo "column in if"
    stty -a |
    awk -F \; '/columns/ { for (i = 1; i <= NF; i++) {
                               if ($i ~ "columns") {
                                   sub(" *columns *= *", "", $i);
                                   print $i;
                                   exit
                               }
                         }
             }' |
    read COLUMNS
fi

center()
{

 echo "In center function"
 echo "COLUMNS : $COLUMNS"
 echo "2 : ${#2}"
    n=$(( ($COLUMNS - ${#2}) / 2 ))
   #n=`expr $COLUMNS - ${#2} / 2`;
    echo "n is $n";
   echo "COLUMNS in center fun : $COLUMNS" ;
    tput cup $1 $n
    echo $_N $2 $_C
}

I know that it is not going in the if condition as the COLUMNS is not blank.Also COLUMNS may vary depending on the size of the window.How do i make the

n=$(( ($COLUMNS - ${#2}) / 2 ))

Work?

Use COLUMNS=$( tput cols ) instead of the awk construct.

Henk Langeveld
– Henk Langeveld

2012-07-14 19:38:24 +00:00
Commented Jul 14, 2012 at 19:38 — Henk Langeveld
– Henk Langeveld, Commented Jul 14, 2012 at 19:38

Dennis Williamson · Accepted Answer · 2012-07-14 06:56:15Z

1

Your echo and your error message seem to hold the clue:

COLUMNS : columns 142

and

/ShellsAndSQLs/task_menu: line 80:  (columns 142 - 13) / 2 : arithmetic syntax error

Where does "columns" (all lower-case) come from? Somehow your variable is getting some text added to it.

That doesn't happen for me in ksh and I don't see where it's happening in your script.

answered Jul 14, 2012 at 6:56

Dennis Williamson

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