Scripts and tools: Use #!/usr/bin/env bash instead of #!/bin/bash. #14831

As it was discussed in #13510, it is better to use #!/usr/bin/env bash instead of #!/bin/bash.

Concept ACK

Take a look at how test/lint/lint-python-shebang.sh enforces the expected shebang for Python scripts.

I thought we had a linter to lint those, but maybe the linters aren't linting themselves.

utACK 50ec1c8

Checked that this is the only occurrence of #!/bin/bash in the code.

In future, please try and preface your commit message, and write a more descriptive message. i.e scripts: Use #!/usr/bin/env bash over obsoleted #!/bin/bash.

This note could be added to developer-notes.md.

@vim88 Could include the dev notes commit from #14846 here and keep these related changes to one PR?

Also, what about adding this:

diff --git a/test/lint/lint-python-shebang.sh b/test/lint/lint-python-shebang.sh
index 4ff87f0bf..3a023fd80 100755
--- a/test/lint/lint-python-shebang.sh
+++ b/test/lint/lint-python-shebang.sh
@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# Shebang must use python3 (not python or python2)
+# Assert expected shebang lines

 export LC_ALL=C
 EXIT_CODE=0
@@ -10,4 +10,10 @@ for PYTHON_FILE in $(git ls-files -- "*.py"); do
         EXIT_CODE=1
     fi
 done
+for SHELL_FILE in $(git ls-files -- "*.sh"); do
+    if [[ $(head -n 1 "${SHELL_FILE}") != "#!/usr/bin/env bash" && $(head -n 1 "${SHELL_FILE}") != "#!/bin/sh" ]]; then
+        echo "Missing expected shebang \"#!/usr/bin/env bash\" or \"#!/bin/sh\" in ${SHELL_FILE}"
+        EXIT_CODE=1
+    fi
+done
 exit ${EXIT_CODE}

And then git mv test/lint/lint-python-shebang.sh test/lint/lint-shebang.sh.

That way we'll never have to think about this ever again :-)

I agree that we should keep all these related changes in this PR.

I commited here the DOC additions from #14846 about Scripts shebang to developer-notes.md.

I also added the linting part for Shell Scripts shebang. (Thanks @practicalswift!)

It seems that the Travis CI build failed for "Lint", so the new linting part for Shell Scripts shebang works.

Missing expected shebang "#!/usr/bin/env bash" or "#!/bin/sh" in contrib/qos/tc.sh
Missing expected shebang "#!/usr/bin/env bash" or "#!/bin/sh" in src/qt/res/movies/makespinner.sh
^---- failure generated from test/lint/lint-shebang.sh

Should I add the shebangs to those two files in this PR? Also, is #!/usr/bin/env bash or #!/bin/sh preffered?

@vim88 Add shebangs to tc.sh and makespinner.sh too. They should have #!/usr/bin/env bash since they use bash features.

I added the missing #!/usr/bin/env bash shebang to contrib/qos/tc.sh and src/qt/res/movies/makespinner.sh.

utACK 114ff903b69513fbfb7a3fc7fd19e6ef6ffa5a7e, but please squash commits

I squashed the commits.

utACK 688f665a5e526fda0fb797bf617412fe9cbe64fd

Fantastic! utACK 688f665

re-utACK 688f665

utACK 688f665

Thank you all!