Loop to print odd numbers not printing as many as it should
I'm writing a script that prints out a user-provided amount of odd numbers starting from a user-provided number.
So for an example if you would enter that you want to print out 5 numbers starting from the number 3, it would output 3, 5, 7, 9, and 11.
I'm currently trying to use the following code:
echo "Enter how many numbers you want to print"
read n
echo "Enter the first number"
read a
for ((a; a < n; a++)); do
((b = a % 2))
if [ $b -ne 0 ]; then
echo "$a"
fi
done
However, with n=5; a=3, the output is not the expected 3 5 7 9 11 but is instead only 3.
bash
edited Nov 22 at 17:41
Charles Duffy
172k25193249
asked Nov 22 at 17:26
Frostbytee
11
add a comment |
I'm writing a script that prints out a user-provided amount of odd numbers starting from a user-provided number.
So for an example if you would enter that you want to print out 5 numbers starting from the number 3, it would output 3, 5, 7, 9, and 11.
I'm currently trying to use the following code:
echo "Enter how many numbers you want to print"
read n
echo "Enter the first number"
read a
for ((a; a < n; a++)); do
((b = a % 2))
if [ $b -ne 0 ]; then
echo "$a"
fi
done
However, with n=5; a=3, the output is not the expected 3 5 7 9 11 but is instead only 3.
bash
edited Nov 22 at 17:41
Charles Duffy
172k25193249
asked Nov 22 at 17:26
Frostbytee
11
...so, what's the part that doesn't actually work? See Minimal, Complete, and Verifiable example guidelines -- a question should have a specific problem (not the larger problem your script tries to solve, but the problem with your script), and the shortest code that lets others see that problem.
– Charles Duffy
Nov 22 at 17:31
BTW, a good place to start is logging withset -x. See your code running at ideone.com/hgCZDP, with a log in the "stderr" section.
– Charles Duffy
Nov 22 at 17:35
2
...in the current case, what you have isn't a bash-the-language bug, but a thinking-about-your-problem bug: You're comparinga < n, butadoesn't start at 0, it starts at the value the user entered, so it doesn't printnnumbers; instead, it just prints odd numbers greater than or equal toaand less thann. For the examplesn=5anda=3, the only odd number that meets that criteria is3, so that's all it prints.
– Charles Duffy
Nov 22 at 17:36
add a comment |
I'm writing a script that prints out a user-provided amount of odd numbers starting from a user-provided number.
So for an example if you would enter that you want to print out 5 numbers starting from the number 3, it would output 3, 5, 7, 9, and 11.
I'm currently trying to use the following code:
echo "Enter how many numbers you want to print"
read n
echo "Enter the first number"
read a
for ((a; a < n; a++)); do
((b = a % 2))
if [ $b -ne 0 ]; then
echo "$a"
fi
done
However, with n=5; a=3, the output is not the expected 3 5 7 9 11 but is instead only 3.
bash
edited Nov 22 at 17:41
Charles Duffy
172k25193249
asked Nov 22 at 17:26
Frostbytee
11
I'm writing a script that prints out a user-provided amount of odd numbers starting from a user-provided number.
So for an example if you would enter that you want to print out 5 numbers starting from the number 3, it would output 3, 5, 7, 9, and 11.
I'm currently trying to use the following code:
echo "Enter how many numbers you want to print"
read n
echo "Enter the first number"
read a
for ((a; a < n; a++)); do
((b = a % 2))
if [ $b -ne 0 ]; then
echo "$a"
fi
done
However, with n=5; a=3, the output is not the expected 3 5 7 9 11 but is instead only 3.
bash
bash
edited Nov 22 at 17:41
Charles Duffy
172k25193249
asked Nov 22 at 17:26
Frostbytee
11
edited Nov 22 at 17:41
Charles Duffy
172k25193249
asked Nov 22 at 17:26
Frostbytee
11
edited Nov 22 at 17:41
Charles Duffy
172k25193249
edited Nov 22 at 17:41
Charles Duffy
172k25193249
edited Nov 22 at 17:41
Charles Duffy
172k25193249
172k25193249
asked Nov 22 at 17:26
Frostbytee
11
asked Nov 22 at 17:26
Frostbytee
11
asked Nov 22 at 17:26
Frostbytee
11
11
...so, what's the part that doesn't actually work? See Minimal, Complete, and Verifiable example guidelines -- a question should have a specific problem (not the larger problem your script tries to solve, but the problem with your script), and the shortest code that lets others see that problem.
– Charles Duffy
Nov 22 at 17:31
BTW, a good place to start is logging withset -x. See your code running at ideone.com/hgCZDP, with a log in the "stderr" section.
– Charles Duffy
Nov 22 at 17:35
2
...in the current case, what you have isn't a bash-the-language bug, but a thinking-about-your-problem bug: You're comparinga < n, butadoesn't start at 0, it starts at the value the user entered, so it doesn't printnnumbers; instead, it just prints odd numbers greater than or equal toaand less thann. For the examplesn=5anda=3, the only odd number that meets that criteria is3, so that's all it prints.
– Charles Duffy
Nov 22 at 17:36
add a comment |
...so, what's the part that doesn't actually work? See Minimal, Complete, and Verifiable example guidelines -- a question should have a specific problem (not the larger problem your script tries to solve, but the problem with your script), and the shortest code that lets others see that problem.
– Charles Duffy
Nov 22 at 17:31
BTW, a good place to start is logging withset -x. See your code running at ideone.com/hgCZDP, with a log in the "stderr" section.
– Charles Duffy
Nov 22 at 17:35
2
...in the current case, what you have isn't a bash-the-language bug, but a thinking-about-your-problem bug: You're comparinga < n, butadoesn't start at 0, it starts at the value the user entered, so it doesn't printnnumbers; instead, it just prints odd numbers greater than or equal toaand less thann. For the examplesn=5anda=3, the only odd number that meets that criteria is3, so that's all it prints.
– Charles Duffy
Nov 22 at 17:36
...so, what's the part that doesn't actually work? See Minimal, Complete, and Verifiable example guidelines -- a question should have a specific problem (not the larger problem your script tries to solve, but the problem with your script), and the shortest code that lets others see that problem.
– Charles Duffy
Nov 22 at 17:31
...so, what's the part that doesn't actually work? See Minimal, Complete, and Verifiable example guidelines -- a question should have a specific problem (not the larger problem your script tries to solve, but the problem with your script), and the shortest code that lets others see that problem.
– Charles Duffy
Nov 22 at 17:31
BTW, a good place to start is logging with
set -x. See your code running at ideone.com/hgCZDP, with a log in the "stderr" section.– Charles Duffy
Nov 22 at 17:35
BTW, a good place to start is logging with
set -x. See your code running at ideone.com/hgCZDP, with a log in the "stderr" section.– Charles Duffy
Nov 22 at 17:35
2
2
...in the current case, what you have isn't a bash-the-language bug, but a thinking-about-your-problem bug: You're comparing
a < n, but a doesn't start at 0, it starts at the value the user entered, so it doesn't print n numbers; instead, it just prints odd numbers greater than or equal to a and less than n. For the examples n=5 and a=3, the only odd number that meets that criteria is 3, so that's all it prints.– Charles Duffy
Nov 22 at 17:36
...in the current case, what you have isn't a bash-the-language bug, but a thinking-about-your-problem bug: You're comparing
a < n, but a doesn't start at 0, it starts at the value the user entered, so it doesn't print n numbers; instead, it just prints odd numbers greater than or equal to a and less than n. For the examples n=5 and a=3, the only odd number that meets that criteria is 3, so that's all it prints.– Charles Duffy
Nov 22 at 17:36
add a comment |
1 Answer
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This is a logic error, rather than a problem using bash. If you want to print n numbers, the easiest way to make sure that happens is to iterate from 0 to n, as follows:
#!/usr/bin/env bash
n=5; a=3 # of course, you can also read from the user.
if ((a % 2 == 0)); then # if our starting number is even...
(( ++a )) # add 1 to make it odd.
fi
for ((i=0; i<n; i++)); do # iterate from 0 to n...
echo "$((a + i*2))" # ...emitting 2*i+a each time.
done
add a comment |
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1 Answer
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1 Answer
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active
oldest
votes
active
oldest
votes
active
oldest
votes
This is a logic error, rather than a problem using bash. If you want to print n numbers, the easiest way to make sure that happens is to iterate from 0 to n, as follows:
#!/usr/bin/env bash
n=5; a=3 # of course, you can also read from the user.
if ((a % 2 == 0)); then # if our starting number is even...
(( ++a )) # add 1 to make it odd.
fi
for ((i=0; i<n; i++)); do # iterate from 0 to n...
echo "$((a + i*2))" # ...emitting 2*i+a each time.
done
add a comment |
This is a logic error, rather than a problem using bash. If you want to print n numbers, the easiest way to make sure that happens is to iterate from 0 to n, as follows:
#!/usr/bin/env bash
n=5; a=3 # of course, you can also read from the user.
if ((a % 2 == 0)); then # if our starting number is even...
(( ++a )) # add 1 to make it odd.
fi
for ((i=0; i<n; i++)); do # iterate from 0 to n...
echo "$((a + i*2))" # ...emitting 2*i+a each time.
done
add a comment |
This is a logic error, rather than a problem using bash. If you want to print n numbers, the easiest way to make sure that happens is to iterate from 0 to n, as follows:
#!/usr/bin/env bash
n=5; a=3 # of course, you can also read from the user.
if ((a % 2 == 0)); then # if our starting number is even...
(( ++a )) # add 1 to make it odd.
fi
for ((i=0; i<n; i++)); do # iterate from 0 to n...
echo "$((a + i*2))" # ...emitting 2*i+a each time.
done
This is a logic error, rather than a problem using bash. If you want to print n numbers, the easiest way to make sure that happens is to iterate from 0 to n, as follows:
#!/usr/bin/env bash
n=5; a=3 # of course, you can also read from the user.
if ((a % 2 == 0)); then # if our starting number is even...
(( ++a )) # add 1 to make it odd.
fi
for ((i=0; i<n; i++)); do # iterate from 0 to n...
echo "$((a + i*2))" # ...emitting 2*i+a each time.
done
edited Nov 22 at 18:27
community wiki
2 revs, 2 users 92%
Charles Duffy
add a comment |
add a comment |
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...so, what's the part that doesn't actually work? See Minimal, Complete, and Verifiable example guidelines -- a question should have a specific problem (not the larger problem your script tries to solve, but the problem with your script), and the shortest code that lets others see that problem.
– Charles Duffy
Nov 22 at 17:31
BTW, a good place to start is logging with
set -x. See your code running at ideone.com/hgCZDP, with a log in the "stderr" section.– Charles Duffy
Nov 22 at 17:35
2
...in the current case, what you have isn't a bash-the-language bug, but a thinking-about-your-problem bug: You're comparing
a < n, butadoesn't start at 0, it starts at the value the user entered, so it doesn't printnnumbers; instead, it just prints odd numbers greater than or equal toaand less thann. For the examplesn=5anda=3, the only odd number that meets that criteria is3, so that's all it prints.– Charles Duffy
Nov 22 at 17:36