By: Dorris in Linux Tutorials on 2011-01-15
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
# Script to test if..elif...else
if [ $1 -gt 0 ]; then
echo "$1 is positive"
elif [ $1 -lt 0 ]
echo "$1 is negative"
elif [ $1 -eq 0 ]
echo "$1 is zero"
echo "Opps! $1 is not number, give number"
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".
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