Check shasum/sha256sum in PATH on install script (babashka#1108)

* Check shasum/sha256sum in PATH on install script

* Fix typo in .github/pull_request_template.md

.github/pull_request_template.md

@@ -2,7 +2,7 @@ Please answer the following questions and leave the below in as part of your PR.
 
 - [ ] I have read the [developer documentation](https://github.com/babashka/babashka/blob/master/doc/dev.md).
 
-- [ ] This PR correponds to an [issue with a clear problem statement](https://github.com/babashka/babashka/blob/master/doc/dev.md#start-with-an-issue-before-writing-code).
+- [ ] This PR corresponds to an [issue with a clear problem statement](https://github.com/babashka/babashka/blob/master/doc/dev.md#start-with-an-issue-before-writing-code).
 
 - [ ] This PR contains a [test](https://github.com/babashka/babashka/blob/master/doc/dev.md#tests) to prevent against future regressions
 

install

@@ -111,14 +111,26 @@ esac
 
 download_url="https://github.com/babashka/babashka/releases/download/v$version/$filename"
 
+# macOS only have shasum available by default
+# Some Linux distros (RHEL-like) only have sha256sum avaiable by default (others have both)
+if command -v sha256sum >/dev/null; then
+   sha256sum_cmd="sha256sum"
+elif command -v shasum >/dev/null; then
+   sha256sum_cmd="shasum -a 256"
+else
+   >&2 echo "Either 'sha256sum' or 'shasum' needs to be on PATH for '--checksum' flag!"
+   >&2 echo "Exiting..."
+   exit 1
+fi
+
 # Running this part in a subshell so when it finishes we go back to the previous directory
 mkdir -p "$download_dir" && (
     cd "$download_dir"
     echo -e "Downloading $download_url to $download_dir"
 
     curl -o "$filename" -sL "$download_url"
     if [[ -n "$checksum" ]]; then
-        if ! echo "$checksum *$filename" | shasum -a 256 --check --status; then
+        if ! echo "$checksum *$filename" | $sha256sum_cmd --check --status; then
             >&2 echo "Failed checksum on $filename"
             >&2 echo "Got: $(shasum -a 256 "$filename" | cut -d' ' -f1)"
             >&2 echo "Expected: $checksum"