CODEWITHSUNDEEP
bashgnu-parallel
a06e
a06e

Reputation: 20774

GNU parallel with variable sequence?

I want to run a program prog in parallel using GNU's parallel, with an argument that takes a value in a sequence. For example:

parallel prog ::: {1..100}

However, I don't know the upper bound of the sequence in advance, so I would like to be able to do something like:

parallel prog ::: {1..$x}

where $x is a number that I'll compute somewhere. How can I achieve this?

Upvotes: 7

Views: 3133

Answers (1)

chepner
chepner

Reputation: 531215

Assuming the seq program (or something like it) is available, 

parallel prog ::: $(seq 1 $x)

If not, you can fake it:

parallel prog ::: $(for ((i=1; i < x; i++)) do; echo $i; done)

As Ole points out, if $x is large, then the resulting sequence of numbers may be too large to fit on the command line. In that case, use either of the two methods above to feed the arguments to parallel via standard input:

seq 1 "$x" | parallel prog
for ((i=1; i<x; i++)) do; echo "$i"; done | parallel prog

Upvotes: 8

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