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I am working on a file where I have columns of very large values.

(like 40 digits : 646512354651316486246729519751795724672467596754627.06843 and so on ...)

I would like to have those numbers in scientific notation but with only 3 or 4 numbers after the dot. Is there a way to use sed or something to do that on every number that appears in my file?

2 Answers 2

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Your shell might have a printf builtin you can use to format numbers.

$ type printf
printf is a shell builtin
$ printf "%.3e\n" 646512354651316486246729519751795724672467596754627.06843
6.465e+50
$ printf "%.4e\n" 646512354651316486246729519751795724672467596754627.06843
6.4651e+50
$ _

If not, there's often a dedicated printf binary, too.

$ which printf
/usr/bin/printf
$ _
9

If you want to convert only specific column, awk helps

$ cat ip.txt
foo 64651235465131648624672951975 123
bar 3452356235235235 xyz
baz 234325236452352352345234532 ijkls

$ # change only second column
$ awk '{$2 = sprintf("%.3e", $2)} 1' ip.txt
foo 6.465e+28 123
bar 3.452e+15 xyz
baz 2.343e+26 ijkls
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