semver -c (--coerce): turn v2, 1.2 or 'nginx/1.27.4' into a valid version

semver -c "v2" prints 2.0.0, semver -c "1.2" prints 1.2.0, and semver -c "nginx/1.27.4 (Ubuntu)" prints 1.27.4: coercion finds the first group of one to three dot-separated numbers in the input and turns it into a valid SemVer MAJOR.MINOR.PATCH, padding missing parts with zero. It is the way to compare versions reported by tools (python --version, openssl version, a Git tag) that are not strict SemVer. Without -c, semver accepts only valid versions and exits with 1 otherwise.

Coercing real-world version strings

node-semver's CLI is installed in a temporary folder (npx semver behaves the same):

npm init -y >/dev/null && npm install --silent --no-audit --no-fund semver@7.8.5 >/dev/null 2>&1
export PATH="$PWD/node_modules/.bin:$PATH"
for v in v2 "version 1.2" 1.2.3.4 "nginx/1.27.4 (Ubuntu)" "Python 3.13.15" "OpenSSL 3.5.7 9 Jun 2026" release-2024.10 1.2.3-beta.1; do
  printf '%-28s -> %s\n' "$v" "$(semver -c "$v")"
done
echo "--- right to left:"; semver -c --rtl 1.2.3.4
echo "--- keep the prerelease with -p:"; semver -c -p "v1.2.3-beta.2+build"
echo "--- without -c:"; semver "version 1.2"; echo "exit $?"
echo "--- nothing to coerce:"; semver -c "latest"; echo "exit $?"
echo "--- coerce, then filter by range:"; semver -c 1.2.3 1.10 2 -r ">=1.5"

v2                           -> 2.0.0
version 1.2                  -> 1.2.0
1.2.3.4                      -> 1.2.3
nginx/1.27.4 (Ubuntu)        -> 1.27.4
Python 3.13.15               -> 3.13.15
OpenSSL 3.5.7 9 Jun 2026     -> 3.5.7
release-2024.10              -> 2024.10.0
1.2.3-beta.1                 -> 1.2.3
--- right to left:
2.3.4
--- keep the prerelease with -p:
1.2.3-beta.2
--- without -c:
exit 1
--- nothing to coerce:
exit 1
--- coerce, then filter by range:
1.10.0
2.0.0

Text around the numbers is ignored, a fourth component is dropped, and a prerelease suffix is removed unless -p is given. A string with no digits at all cannot be coerced: semver prints nothing and exits with 1. Combined with -r, every argument is coerced first and then filtered by the range.

Rules of coercion

When to use it, and when not

Coercion is ideal for "is the installed tool new enough?" checks:

have=$(semver -c "$(openssl version)")
semver -r ">=3.0.0" "$have" >/dev/null || echo "OpenSSL 3 required, found $have"

Do not use it to validate input that is supposed to be SemVer (package versions, release tags): coercion happily turns 1.2.3.4-hotfix or v2-final into something valid and hides the mistake. Validate strictly instead, as on validate a SemVer string, and handle the library's TypeError: Invalid Version.

Pitfalls

• Date-like versions. release-2024.10 becomes 2024.10.0, which sorts correctly against other dates but is not a semantic version in spirit.
• Leading zeros. v01.02.03 is not coerced in node-semver 7.8 (it prints nothing); strip the zeros first.
• Shell comparison. For simple numeric comparisons without Node, sort -V is an alternative; see compare two versions in bash. For malformed but nearly valid versions, semver -l may be the better choice.

FAQ