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Project Notes

Sort by Numbers

Sorting text numerically in the shell using the special “version sort” mode of the sort utility.

Notes

Version strings and other text with embedded integers don’t sort nicely by default, so natural alphabetical sorting will mess us up.

Generating some version numbers to be sorted:

$ printf "v1.%d.0\n" $(seq 20 -1 0) > version_strings.txt
$ cat version_strings.txt
v1.20.0
v1.19.0
v1.18.0
v1.17.0
v1.16.0
v1.15.0
v1.14.0
v1.13.0
v1.12.0
v1.11.0
v1.10.0
v1.9.0
v1.8.0
v1.7.0
v1.6.0
v1.5.0
v1.4.0
v1.3.0
v1.2.0
v1.1.0
v1.0.0

Piping this through sort mixes this up as would be expected:

$ cat version_strings.txt | sort
v1.0.0
v1.1.0
v1.10.0
v1.11.0
v1.12.0
v1.13.0
v1.14.0
v1.15.0
v1.16.0
v1.17.0
v1.18.0
v1.19.0
v1.2.0
v1.20.0
v1.3.0
v1.4.0
v1.5.0
v1.6.0
v1.7.0
v1.8.0
v1.9.0

Howerver sort has a special “version sort” mode --version-sort or -V that magically handles this correctly:

$ cat version_strings.txt | sort -V
v1.0.0
v1.1.0
v1.2.0
v1.3.0
v1.4.0
v1.5.0
v1.6.0
v1.7.0
v1.8.0
v1.9.0
v1.10.0
v1.11.0
v1.12.0
v1.13.0
v1.14.0
v1.15.0
v1.16.0
v1.17.0
v1.18.0
v1.19.0
v1.20.0

Although intend for sorting version srtings, it handles many simple integer sort tasks:

$ printf "dog-%d.txt\n" $(seq 20 -1 0) > numbered_strings.txt
$ printf "cat-%d.txt\n" $(seq 20 -1 0) >> numbered_strings.txt
$ cat numbered_strings.txt
dog-20.txt
dog-19.txt
dog-18.txt
dog-17.txt
dog-16.txt
dog-15.txt
dog-14.txt
dog-13.txt
dog-12.txt
dog-11.txt
dog-10.txt
dog-9.txt
dog-8.txt
dog-7.txt
dog-6.txt
dog-5.txt
dog-4.txt
dog-3.txt
dog-2.txt
dog-1.txt
dog-0.txt
cat-20.txt
cat-19.txt
cat-18.txt
cat-17.txt
cat-16.txt
cat-15.txt
cat-14.txt
cat-13.txt
cat-12.txt
cat-11.txt
cat-10.txt
cat-9.txt
cat-8.txt
cat-7.txt
cat-6.txt
cat-5.txt
cat-4.txt
cat-3.txt
cat-2.txt
cat-1.txt
cat-0.txt

Sorting by version produces the expected result:

$ cat numbered_strings.txt | sort -V
cat-0.txt
cat-1.txt
cat-2.txt
cat-3.txt
cat-4.txt
cat-5.txt
cat-6.txt
cat-7.txt
cat-8.txt
cat-9.txt
cat-10.txt
cat-11.txt
cat-12.txt
cat-13.txt
cat-14.txt
cat-15.txt
cat-16.txt
cat-17.txt
cat-18.txt
cat-19.txt
cat-20.txt
dog-0.txt
dog-1.txt
dog-2.txt
dog-3.txt
dog-4.txt
dog-5.txt
dog-6.txt
dog-7.txt
dog-8.txt
dog-9.txt
dog-10.txt
dog-11.txt
dog-12.txt
dog-13.txt
dog-14.txt
dog-15.txt
dog-16.txt
dog-17.txt
dog-18.txt
dog-19.txt
dog-20.txt

Credits and References

About LCK#176 Bash
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This page is a web-friendly rendering of my project notes shared in the LittleCodingKata GitHub repository.

LittleCodingKata is my collection of programming exercises, research and code toys broadly spanning things that relate to programming and software development (languages, frameworks and tools).

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