QNX shell loop sequence

Question

Both following examples work in modern Bash but don't work in different sh shells (like QNX shell).

$ for i in {1..3}; do echo $i; done
1
2
3

$ for i in $(seq 1 3); do echo $i; done
1
2
3

Is there any alternative method to produce same sequence in QNX shell?

Which QNX shell? Which version of QNX? The docs say ksh is the current shell. — Dennis Williamson, Jun 25 '12 at 11:30

score 1 · Accepted Answer · answered Jun 27 '12 at 08:27

1

I found a method which works in QNX shell:

integer i=0
while ((i<4)); do i=i+1; echo $i; done

answered Jun 27 '12 at 08:27

psihodelia

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This works, but `for ((i = 1; i <=3; i++ ))` doesn't? Is this QNX 4? What is it running on? – Dennis Williamson Jun 27 '12 at 10:42

score 1 · Answer 2 · answered Jun 27 '12 at 08:55

1

Here is a simple workaround to simulate the expr hack.

yes |
head -n 3 |
nl |
while read i yes; do
  ....
done

If you don't care about the value of i you can take out the nl line numbering.

answered Jun 27 '12 at 08:55

tripleee

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+1 Nice technique. I imagine if `expr` is missing, `nl` and/or `yes` is probably missing as well, though. – William Pursell Jun 27 '12 at 12:01

Dennis Williamson · Answer 3 · 2012-06-25T13:54:13.047

0

Use seq or jot. You may need to use backticks instead of $().

for i in `seq 1 3`

If the shell in the version of QNX you're using is ksh, then you should be able to use C-style for loops:

for ((i = 1; i <=3; i++ ))

Edit:

I'm now guessing that you have QNX 4 which has a ksh86 clone as its shell. In my opinion, under these circumstances, it is brain dead to not include seq or jot. However, all that aside, here is a hack that should be able to do sequences:

end=3
for n in $(echo "for (i = 1; i <= $end; i++) i" | bc)
do
    echo "$n"
done

edited Jun 25 '12 at 13:54

answered Jun 25 '12 at 11:20

Dennis Williamson

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@psihodelia: `seq` is not in any shell that I'm aware of. It's an external utility. – Dennis Williamson Jun 25 '12 at 11:22
Yes, sure, but my question is "Is there any alternative method to produce same sequence in QNX shell?" – psihodelia Jun 25 '12 at 11:23
# for ((i = 1; i <=3; i++ )) sh: syntax error: `((' unexpected – psihodelia Jun 25 '12 at 12:07
@psihodelia: What does `echo "$((3 + 4))` output? – Dennis Williamson Jun 25 '12 at 13:40
It doesn't work cause my QNX has no bc tool. But echo "$((3 + 4))" prints 7 – psihodelia Jun 27 '12 at 08:17

score 0 · Answer 4 · answered Jun 25 '12 at 16:38

0

Any posix compliant shell will allow you to iterate:

i=1
while expr $i \< 4 > /dev/null; do
  echo $i
  : $(( i + 1 ))
done

If you have an older shell, you may need to replace the last line inside the loop with i=$( expr $i + 1 ), and in some rare instances you may need to use back ticks.

answered Jun 25 '12 at 16:38

William Pursell

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Thank you, looks like the right direction. But my shell doesn't have 'expr' tool. Is there any other method to substitute expr'? – psihodelia Jun 27 '12 at 08:14

score 0 · Answer 5 · answered Sep 06 '16 at 16:00

0

You can get bash for QNX from the NetBSD pkgsrc repository: ftp://ftp.netbsd.org/pub/pkgsrc/packages/QNX/i386/6.5.0_head_20110826/shells/

answered Sep 06 '16 at 16:00

Whome

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QNX shell loop sequence

5 Answers5