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How do I exit BASH while loop using modulus operator?

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4

So practically for my assignment I need to break out of a true while loop when the user inputs a number that gives a modulus remainder of 0, ex: (25 % 5 = 0 break loop) Where in my attempt below have I gone wrong?

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 else
 echo "you entered right"
 break
fi
done

command-line bash scripts

share|improve this question

edited 2 days ago

Roosevelt Mendieta

asked 2 days ago

Roosevelt MendietaRoosevelt Mendieta

4915

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  If the assignment specifies bash, then you might consider using its built-in arithmetic expansion syntax e.g. (( INPUT % 5 == 0 ))
  
  – steeldriver
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  the loop does not end when entering 25 @steeldriver
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  

add a comment | 

4

So practically for my assignment I need to break out of a true while loop when the user inputs a number that gives a modulus remainder of 0, ex: (25 % 5 = 0 break loop) Where in my attempt below have I gone wrong?

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 else
 echo "you entered right"
 break
fi
done

command-line bash scripts

share|improve this question

edited 2 days ago

Roosevelt Mendieta

asked 2 days ago

Roosevelt MendietaRoosevelt Mendieta

4915

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  If the assignment specifies bash, then you might consider using its built-in arithmetic expansion syntax e.g. (( INPUT % 5 == 0 ))
  
  – steeldriver
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  the loop does not end when entering 25 @steeldriver
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  

add a comment | 

So practically for my assignment I need to break out of a true while loop when the user inputs a number that gives a modulus remainder of 0, ex: (25 % 5 = 0 break loop) Where in my attempt below have I gone wrong?

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 else
 echo "you entered right"
 break
fi
done

command-line bash scripts

share|improve this question

edited 2 days ago

Roosevelt Mendieta

asked 2 days ago

Roosevelt MendietaRoosevelt Mendieta

4915

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 else
 echo "you entered right"
 break
fi
done

share|improve this question

edited 2 days ago

Roosevelt Mendieta

asked 2 days ago

Roosevelt MendietaRoosevelt Mendieta

4915

share|improve this question

edited 2 days ago

Roosevelt Mendieta

asked 2 days ago

Roosevelt MendietaRoosevelt Mendieta

4915

asked 2 days ago

Roosevelt MendietaRoosevelt Mendieta

4915

asked 2 days ago

Roosevelt MendietaRoosevelt Mendieta

4915

4 Answers
4

active

oldest

votes

7

Move the break from the else part to the if part:

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 break
 else
 echo "you entered right"
 fi
done

share|improve this answer

answered 2 days ago

PerlDuckPerlDuck

7,94611636

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  this doesn't work, when I enter 40 the code exits
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  
  @RooseveltMendieta Isn't it what you want? I need to break out of a true while loop when the user inputs a number that gives a modulus remainder of 0. 40%5 is also 0.
  
  – Kulfy
  2 days ago
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  @Kulfy i was thinking of division in my head instead of modulus, how embarrassing lol yes this solution in fact does work and is exactly what I needed. I need to go to sleep i've been up to late working on this assignment.
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @RooseveltMendieta It seems that you changed the original code in your question. So, PerlDuck might need to modify explanation of the answer.
  
  – Kulfy
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i version controlled the code back to it's original state @Kulfy
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  

add a comment | 

5

It works for me according to @steeldriver's tips,

• 
  

  make sure you use bash

  
  
  

  #!/bin/bash
  

  
  


• 
  

  use the bash syntax for arithmetic evaluation

  
  
  

  ((...))
  

  
  

Otherwise the shellscript can remain the same,

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if (( INPUT % 5 == 0 )) ; then
 echo "you entered right"
 break
 else
 echo "you entered wrong"
 fi
done

Edit: You have modified the question. This answer corresponds to a previous version of the question. (It is not clear to me, if you want to break the loop, when there is no remainder or when there is a remainder.)

share|improve this answer

edited 2 days ago

answered 2 days ago

sudodussudodus

25.7k33078

add a comment | 

4

Since this is bash script we're talking about, you may want to use read -p and arithmetic evaluation ((...))

$ while read -p "Enter number:" input ; do (( input%5 == 0 )) && echo "Wrong"; break; || echo "alright"; done
Enter number:11
alright
Enter number:7
alright
Enter number:10
Wrong

Portably, you might want to use [ aka test

$ [ $((25%5)) -eq 0 ] && echo "Zero"
Zero
$ [ $((26%5)) -eq 0 ] && echo "Zero"
$

share|improve this answer

edited 2 days ago

answered 2 days ago

Sergiy KolodyazhnyySergiy Kolodyazhnyy

74.9k9155326

add a comment | 

0

There is also an example for trap's usage in Bash-Beginners-Guide

You can use trap to catch signal to exit your process or whatever you want.

#!/bin/bash
# traptest.sh

trap "echo Booh!;exit" SIGINT SIGTERM
echo "pid is $$"

while : # This is the same as "while true".
do
 sleep 60 # This script is not really doing anything.
done 

share|improve this answer

answered yesterday

ChingKun YuChingKun Yu

1

New contributor

ChingKun Yu is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  OP's question is basically an assignment, so they do have to use modulo operator and arithmetic, so your answer misses that. Since you're new on the site, I won't downvote the answer, but I suggest you address that part soon. There's many other ways in which you could do arithmetic in Bash, so consider addressing one of them not already mentioned
  
  – Sergiy Kolodyazhnyy
  yesterday
  

  
  
  
  

add a comment | 

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7

Move the break from the else part to the if part:

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 break
 else
 echo "you entered right"
 fi
done

share|improve this answer

answered 2 days ago

PerlDuckPerlDuck

7,94611636

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  this doesn't work, when I enter 40 the code exits
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  
  @RooseveltMendieta Isn't it what you want? I need to break out of a true while loop when the user inputs a number that gives a modulus remainder of 0. 40%5 is also 0.
  
  – Kulfy
  2 days ago
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  @Kulfy i was thinking of division in my head instead of modulus, how embarrassing lol yes this solution in fact does work and is exactly what I needed. I need to go to sleep i've been up to late working on this assignment.
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @RooseveltMendieta It seems that you changed the original code in your question. So, PerlDuck might need to modify explanation of the answer.
  
  – Kulfy
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i version controlled the code back to it's original state @Kulfy
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  

add a comment | 

7

Move the break from the else part to the if part:

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 break
 else
 echo "you entered right"
 fi
done

share|improve this answer

answered 2 days ago

PerlDuckPerlDuck

7,94611636

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  this doesn't work, when I enter 40 the code exits
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  
  @RooseveltMendieta Isn't it what you want? I need to break out of a true while loop when the user inputs a number that gives a modulus remainder of 0. 40%5 is also 0.
  
  – Kulfy
  2 days ago
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  @Kulfy i was thinking of division in my head instead of modulus, how embarrassing lol yes this solution in fact does work and is exactly what I needed. I need to go to sleep i've been up to late working on this assignment.
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @RooseveltMendieta It seems that you changed the original code in your question. So, PerlDuck might need to modify explanation of the answer.
  
  – Kulfy
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i version controlled the code back to it's original state @Kulfy
  
  – Roosevelt Mendieta
  2 days ago
  

  
  
  
  

add a comment | 

Move the break from the else part to the if part:

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 break
 else
 echo "you entered right"
 fi
done

share|improve this answer

answered 2 days ago

PerlDuckPerlDuck

7,94611636

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if [ `expr $INPUT % 5` -eq 0 ]; then
 echo "you entered wrong"
 break
 else
 echo "you entered right"
 fi
done

share|improve this answer

answered 2 days ago

PerlDuckPerlDuck

7,94611636

answered 2 days ago

PerlDuckPerlDuck

7,94611636

answered 2 days ago

PerlDuckPerlDuck

7,94611636

5

It works for me according to @steeldriver's tips,

• 
  

  make sure you use bash

  
  
  

  #!/bin/bash
  

  
  


• 
  

  use the bash syntax for arithmetic evaluation

  
  
  

  ((...))
  

  
  

Otherwise the shellscript can remain the same,

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if (( INPUT % 5 == 0 )) ; then
 echo "you entered right"
 break
 else
 echo "you entered wrong"
 fi
done

Edit: You have modified the question. This answer corresponds to a previous version of the question. (It is not clear to me, if you want to break the loop, when there is no remainder or when there is a remainder.)

share|improve this answer

edited 2 days ago

answered 2 days ago

sudodussudodus

25.7k33078

add a comment | 

5

It works for me according to @steeldriver's tips,

• 
  

  make sure you use bash

  
  
  

  #!/bin/bash
  

  
  


• 
  

  use the bash syntax for arithmetic evaluation

  
  
  

  ((...))
  

  
  

Otherwise the shellscript can remain the same,

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if (( INPUT % 5 == 0 )) ; then
 echo "you entered right"
 break
 else
 echo "you entered wrong"
 fi
done

Edit: You have modified the question. This answer corresponds to a previous version of the question. (It is not clear to me, if you want to break the loop, when there is no remainder or when there is a remainder.)

share|improve this answer

edited 2 days ago

answered 2 days ago

sudodussudodus

25.7k33078

add a comment | 

It works for me according to @steeldriver's tips,

• 
  

  make sure you use bash

  
  
  

  #!/bin/bash
  

  
  


• 
  

  use the bash syntax for arithmetic evaluation

  
  
  

  ((...))
  

  
  

Otherwise the shellscript can remain the same,

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if (( INPUT % 5 == 0 )) ; then
 echo "you entered right"
 break
 else
 echo "you entered wrong"
 fi
done

Edit: You have modified the question. This answer corresponds to a previous version of the question. (It is not clear to me, if you want to break the loop, when there is no remainder or when there is a remainder.)

share|improve this answer

edited 2 days ago

answered 2 days ago

sudodussudodus

25.7k33078

#!/bin/bash

while true
do
 echo "Please input anything here: "
 read INPUT

 if (( INPUT % 5 == 0 )) ; then
 echo "you entered right"
 break
 else
 echo "you entered wrong"
 fi
done

share|improve this answer

edited 2 days ago

answered 2 days ago

sudodussudodus

25.7k33078

answered 2 days ago

sudodussudodus

25.7k33078

answered 2 days ago

sudodussudodus

25.7k33078

4

Since this is bash script we're talking about, you may want to use read -p and arithmetic evaluation ((...))

$ while read -p "Enter number:" input ; do (( input%5 == 0 )) && echo "Wrong"; break; || echo "alright"; done
Enter number:11
alright
Enter number:7
alright
Enter number:10
Wrong

Portably, you might want to use [ aka test

$ [ $((25%5)) -eq 0 ] && echo "Zero"
Zero
$ [ $((26%5)) -eq 0 ] && echo "Zero"
$

share|improve this answer

edited 2 days ago

answered 2 days ago

Sergiy KolodyazhnyySergiy Kolodyazhnyy

74.9k9155326

add a comment | 

4

Since this is bash script we're talking about, you may want to use read -p and arithmetic evaluation ((...))

$ while read -p "Enter number:" input ; do (( input%5 == 0 )) && echo "Wrong"; break; || echo "alright"; done
Enter number:11
alright
Enter number:7
alright
Enter number:10
Wrong

Portably, you might want to use [ aka test

$ [ $((25%5)) -eq 0 ] && echo "Zero"
Zero
$ [ $((26%5)) -eq 0 ] && echo "Zero"
$

share|improve this answer

edited 2 days ago

answered 2 days ago

Sergiy KolodyazhnyySergiy Kolodyazhnyy

74.9k9155326

add a comment | 

Since this is bash script we're talking about, you may want to use read -p and arithmetic evaluation ((...))

$ while read -p "Enter number:" input ; do (( input%5 == 0 )) && echo "Wrong"; break; || echo "alright"; done
Enter number:11
alright
Enter number:7
alright
Enter number:10
Wrong

Portably, you might want to use [ aka test

$ [ $((25%5)) -eq 0 ] && echo "Zero"
Zero
$ [ $((26%5)) -eq 0 ] && echo "Zero"
$

share|improve this answer

edited 2 days ago

answered 2 days ago

Sergiy KolodyazhnyySergiy Kolodyazhnyy

74.9k9155326

$ while read -p "Enter number:" input ; do (( input%5 == 0 )) && echo "Wrong"; break; || echo "alright"; done
Enter number:11
alright
Enter number:7
alright
Enter number:10
Wrong

$ [ $((25%5)) -eq 0 ] && echo "Zero"
Zero
$ [ $((26%5)) -eq 0 ] && echo "Zero"
$

share|improve this answer

edited 2 days ago

answered 2 days ago

Sergiy KolodyazhnyySergiy Kolodyazhnyy

74.9k9155326

answered 2 days ago

Sergiy KolodyazhnyySergiy Kolodyazhnyy

74.9k9155326

answered 2 days ago

Sergiy KolodyazhnyySergiy Kolodyazhnyy

74.9k9155326

0

There is also an example for trap's usage in Bash-Beginners-Guide

You can use trap to catch signal to exit your process or whatever you want.

#!/bin/bash
# traptest.sh

trap "echo Booh!;exit" SIGINT SIGTERM
echo "pid is $$"

while : # This is the same as "while true".
do
 sleep 60 # This script is not really doing anything.
done 

share|improve this answer

answered yesterday

ChingKun YuChingKun Yu

1

New contributor

ChingKun Yu is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  OP's question is basically an assignment, so they do have to use modulo operator and arithmetic, so your answer misses that. Since you're new on the site, I won't downvote the answer, but I suggest you address that part soon. There's many other ways in which you could do arithmetic in Bash, so consider addressing one of them not already mentioned
  
  – Sergiy Kolodyazhnyy
  yesterday
  

  
  
  
  

add a comment | 

0

There is also an example for trap's usage in Bash-Beginners-Guide

You can use trap to catch signal to exit your process or whatever you want.

#!/bin/bash
# traptest.sh

trap "echo Booh!;exit" SIGINT SIGTERM
echo "pid is $$"

while : # This is the same as "while true".
do
 sleep 60 # This script is not really doing anything.
done 

share|improve this answer

answered yesterday

ChingKun YuChingKun Yu

1

New contributor

ChingKun Yu is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  OP's question is basically an assignment, so they do have to use modulo operator and arithmetic, so your answer misses that. Since you're new on the site, I won't downvote the answer, but I suggest you address that part soon. There's many other ways in which you could do arithmetic in Bash, so consider addressing one of them not already mentioned
  
  – Sergiy Kolodyazhnyy
  yesterday
  

  
  
  
  

add a comment | 

There is also an example for trap's usage in Bash-Beginners-Guide

You can use trap to catch signal to exit your process or whatever you want.

#!/bin/bash
# traptest.sh

trap "echo Booh!;exit" SIGINT SIGTERM
echo "pid is $$"

while : # This is the same as "while true".
do
 sleep 60 # This script is not really doing anything.
done 

share|improve this answer

answered yesterday

ChingKun YuChingKun Yu

1

New contributor

ChingKun Yu is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

#!/bin/bash
# traptest.sh

trap "echo Booh!;exit" SIGINT SIGTERM
echo "pid is $$"

while : # This is the same as "while true".
do
 sleep 60 # This script is not really doing anything.
done 

share|improve this answer

answered yesterday

ChingKun YuChingKun Yu

1

New contributor

ChingKun Yu is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered yesterday

ChingKun YuChingKun Yu

1

New contributor

ChingKun Yu is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered yesterday

ChingKun YuChingKun Yu

1