Compare two version numbers in bash (is version A greater than B?)

The portable way to compare two version numbers in a bash script is GNU version sort: printf '%s\n' "$a" "$b" | sort -V -C exits with 0 when $a is lower than or equal to $b, because -C checks that the input is already in order. It handles 1.10.0 versus 1.9.0 correctly. For versions with pre-release tags (1.2.0-rc.1), sort -V gets the order wrong; use a SemVer-aware tool such as npx semver or Python's semver package.

Helper functions with sort -V

version_le() { printf '%s\n' "$1" "$2" | sort -V -C; }
version_ge() { version_le "$2" "$1"; }
version_lt() { [ "$1" != "$2" ] && version_le "$1" "$2"; }
for pair in "1.9.0 1.10.0" "2.0.0 2.0.0" "3.1 3.0.9" "1.2.0-rc.1 1.2.0"; do
  set -- $pair
  version_lt "$1" "$2" && echo "$1 <  $2" || { version_le "$2" "$1" && [ "$1" != "$2" ] && echo "$1 >  $2" || echo "$1 == $2"; }
done
echo "--- string comparison gets it wrong"
[[ 1.10.0 > 1.9.0 ]] && echo "1.10.0 > 1.9.0" || echo "string compare says 1.10.0 < 1.9.0"

1.9.0 <  1.10.0
2.0.0 == 2.0.0
3.1 >  3.0.9
1.2.0-rc.1 >  1.2.0
--- string comparison gets it wrong
string compare says 1.10.0 < 1.9.0

The last pair shows the limit: by SemVer rules 1.2.0-rc.1 is lower than 1.2.0, but sort -V puts the shorter string first and reports the opposite.

SemVer-aware comparison

a=1.2.0-rc.1 b=1.2.0
echo "npx semver -r:    $(npx -y semver@7 -r "<$b" "$a" >/dev/null && echo "$a < $b" || echo "no match")"
echo "npx semver -p -r: $(npx -y semver@7 -p -r "<$b" "$a" >/dev/null && echo "$a < $b" || echo "no match")"
uv run -q --no-project --python 3.13 --with semver==3.0.4 python -c '
import sys, semver
a, b = sys.argv[1], sys.argv[2]
print("Version.parse(a).compare(b):", semver.Version.parse(a).compare(b))
print("Version.parse(a) < b:", semver.Version.parse(a) < b)' "$a" "$b"

npx semver -r:    no match
npx semver -p -r: 1.2.0-rc.1 < 1.2.0
Version.parse(a).compare(b): -1
Version.parse(a) < b: True

npx semver -r RANGE VERSION prints the version and exits with 0 when it satisfies the range, so -r "<$b" works as a less-than test. By default, though, a pre-release version matches a range only if one of its comparators has a pre-release tag on the same MAJOR.MINOR.PATCH; <1.2.0 has none, so the first test reports no match. -p (--include-prerelease) turns that rule off and gives the SemVer answer. Version.compare returns -1, 0 or 1, and Version objects also support <, == and > against strings.

Options

Pitfalls

• Invalid input fails differently per tool. sort -V compares anything; semver.Version.parse("1.2") raises ValueError: 1.2 is not valid SemVer string; npx semver prints nothing and exits with 1.
• Strip a leading v from git tags with ${tag#v} before comparing, unless every value has it.
• Build metadata is ignored for precedence. 1.0.0+a and 1.0.0+b compare equal in SemVer tools, but differ as strings and in sort -V.
• set -- $pair splits on spaces. It is used here to unpack test pairs; in real scripts pass the two versions as separate arguments.

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