Multilevel if-then-else in Linux Shell Script
By: Dorris
Syntax: if condition
then
condition is zero (true - 0)
execute all commands up to elif statement
elif condition1
then
condition1 is zero (true - 0)
execute all commands up to elif statement
elif condition2
then
condition2 is zero (true - 0)
execute all commands up to elif statement
else
None of the above condtion,condtion1,condtion2 are true (i.e.
all of the above nonzero or false)
execute all commands up to fi
fi
For multilevel if-then-else statement try the following script:
$ cat > elf
#
#!/bin/sh
# Script to test if..elif...else
#
if [ $1 -gt 0 ]; then
echo "$1 is positive"
elif [ $1 -lt 0 ]
then
echo "$1 is negative"
elif [ $1 -eq 0 ]
then
echo "$1 is zero"
else
echo "Opps! $1 is not number, give number"
fi
Try above script as follows:
$ chmod 755 elf
$ ./elf 1
$ ./elf -2
$ ./elf 0
$ ./elf a
Here o/p for last sample run:
./elf: [: -gt: unary operator expected
./elf: [: -lt: unary operator expected
./elf: [: -eq: unary operator expected
Opps! a is not number, give number
Above program gives error for last run, here integer comparison is expected
therefore error like "./elf: [: -gt: unary operator expected"
occurs, but still our program notify this error to user by providing message
"Oopps! a is not number, give number".
Archived Comments
1. CharlesTig
View Tutorial By: CharlesTig at 2017-06-28 20:48:32
Comment on this tutorial
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