Unix bash. Loop over pairs of incremental integers [duplicate]

Question

I have a program GG that needs two integers as arguments for parameters x and y as input, in this way:

./GG -x 0 -y 100

I need to run GG over sequential start/end pairs of integers, like the pairs in each row here:

x y 0 100 100 200 200 300 ... ... 10000 10100

The closest I get would be something like this:

for i in {0..10000}; do for j in {100..10100}; do ./GG -x ${i} -y ${j}; done; done

but this will loop each j value over each i value, and this is not what I need.

Any suggestion is very welcome !

Hmm. Part of this is a duplicate of How to produce a range with step n in bash to generate a sequence of numbers with; I haven't yet identified a good duplicate for the rest. — Charles Duffy
– Charles Duffy, Commented Jun 27, 2019 at 23:35

Charles Duffy · Accepted Answer · 2019-06-27 23:27:01Z

3

There's no need to loop over two values. Loop over one, but add your offset to it to get the other.

for ((i=0; i<=10000; i+=100)); do ./GG -x "$i" -y "$(( i + 100 ))" done

See this running at https://ideone.com/r3qBZU

See the C-style for loop, and arithmetic expression syntax.

answered Jun 27, 2019 at 23:27

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Charles Duffy

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5 Comments

Lucas Over a year ago

Thanks very much @Charles Duffy !. I know it is a different question, but do you know by chance how to run GG over each pair of values using parallelization instead of waiting until each loop finishes?

Charles Duffy Over a year ago

for ((i=0; i<=10000; i+=100)); do printf '%s\0' "$i"; done | xargs -0 -P 8 -n 8 sh -c 'for arg; do ./GG -x "$arg" -y "$((arg + 100))"; done' _

is one approach. Which, by the way, is already in the knowledgebase if you searched for it.

Charles Duffy Over a year ago

(the -P 8 is number of processes to run at once, the -n 8 is number of items to handle by each process instance before it's restarted with a different group of numbers; tune to fit your hardware, tolerance for overhead, etc).

Lucas Over a year ago

Hi @Charles Duffy, my very last question, apologies. The real GG program takes several arguments: GG -h -l -k -int. The parameter -int uses two integers, like those I mentioned (e.g. GG -h -l -k -int 0 100; GG -h -l -k -int 100 200; etc.). I am not sure if this adjusted script would be the correct one: for ((i=0; i<=10000; i+=100)); do printf '%s\0' "$i"; done | xargs -0 -P 8 -n 8 sh -c 'for arg; do ./GG -h 5 -l 10 -k 1000 -int "$arg" "$((arg + 100))"; done' _

Charles Duffy Over a year ago

@Lucas, at a glance, it looks about right to me. That said, change it from sh -c to sh -x -c, and it'll print a log of the commands it's actually running so you can compare.

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