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Likso
Asked: 2010-06-29 07:01:34 +0800 CST

Shell scripting and regex: Which one is better to match numbers, [[:digit:]] or [0-9]?

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As the title suggests, which one is better to match numbers, [[:digit:]] or [0-9]?

I'm using the bash shell

Thanks :)

bash regular-expressions unix-shell

2 Answers

  1. Best Answer

    The only reason that [[:digit:]] must be used is to support locales that use digits other than 0-9. For example Arabic-Indic Numerals: ٠١٢٣٤٥٦٧٨٩ (Unicode U+0660 through U+0669). Otherwise for the Hindu-Arabic numerals 0123456789, [0-9] works equally as well as [[:digit:]].

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  2. # time grep -oE '[[:digit:]]' /etc/services
...
real    0m0.029s
user    0m0.017s
sys     0m0.013s


# time grep -oE '[0-9]' /etc/services
...
real    0m0.029s
user    0m0.016s
sys     0m0.012s

    I could probably write a quick script to average them, and I bet I'd find that the averages are identical, but it certainly gives you the idea.

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