Question

9

Arithmetic binary operators -gt, -lt give error but work in a shell script

rated 0 times [ 9] [ 0] / answers: 1 / hits: 1773 / 2 Years ago, tue, february 1, 2022, 1:19:21

I wrote this simple script it works too but shows an error

clear

echo Enter 1st number

read n1

echo Enter 2nd number

read n2

echo MUlti is `expr $n1 * $n2`;

if [$n1 -lt $n2]

then

 echo $n1 'is bigger than' $n2

else

 echo $n2 'is bigger than' $n1

fi

output

Enter 1st number

5

Enter 2nd number

10

MUlti is 50

./script.sh: line 7: [5: command not found

10 is bigger than 5

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

damomnning

Add To Favorites

Follow

Total Points: 422

Total Questions: 90

Total Answers: 106

Location: Mali

Member since Thu, Aug 13, 2020

4 Years ago

damomnning questions

1 Slow installation of 22.04 under WSL

Sat, Jul 31, 21, 23:11, 3 Years ago

1 Workspace switching independently ,ubuntu 22 with multiple monitors

Sat, Oct 1, 22, 19:12, 2 Years ago

1 How can I make automatic, full system backups of Ubuntu during normal use (like Macrium Reflect for Windows)

Mon, May 23, 22, 06:50, 2 Years ago

1 is it possible to create symbolic links on exfat filesystem?

Sat, Oct 15, 22, 15:50, 2 Years ago

1 how to find the jobs run by each local users

Tue, Sep 7, 21, 20:23, 3 Years ago

View All

answered 2 Years ago aradxalte · Accepted Answer

The [ is a command builtin, also known as test, and as all commands requires at least a space to separate it from other words in the command. [ is also available as a regular command in /usr/bin/[ or /usr/bin/test.

The presence of a final ] is instead a requirement of the command, when invoked as [, and the spaces around it are required as for every parameter of a command.

That said, in bash you should use the command [[, that has some avantages over [, like for example supporting && and || for logical operations, beside -a and -o.

Moreover, to do integer arithmetic operations and comparison between integers it is better to use arithmetic expansions $((math operations)), and the corresponding command ((math ops)).

With these observations, your script could be:

#!/bin/bash



clear

echo "Enter 1st number"

read n1

echo "Enter 2nd number"

read n2

echo "Multi is $((n1 * n2))"

if ((n1 > n2)); then

  echo "$n1 is bigger than $n2"

else

  echo "$n2 is bigger than $n1"

fi

Remember to make it executable (chmod +x my-script), then execute it with ./my-script.