[ptxdist] [PATCH 4/6] ptxdist: don't depend on bash being /bin/bash

[Ladislav Michl <oss-lists@triops.cz>]

From: Ladislav Michl <ladis@triops.cz>

Provide a helpful message instead of 'bad interpreter' and check
bash version.

Signed-off-by: Ladislav Michl <ladis@triops.cz>
---
 bin/ptxdist              | 24 +++++++++++++++++++++++-
 bin/ptxdist-auto-version |  4 ++--
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/bin/ptxdist b/bin/ptxdist
index 7b20026bb..3c86aa225 100755
--- a/bin/ptxdist
+++ b/bin/ptxdist
@@ -1,4 +1,26 @@
-#!/bin/bash
+#!/bin/sh
+
+#
+# Everything up to the bash version check must be plain POSIX sh: PTXdist
+# may be started by any shell and re-executes itself with bash.
+#
+if [ -z "${BASH_VERSION}" ]; then
+	bash="$(command -v bash)" || {
+		echo "ptxdist: error: bash >= 4.2 is required, please install it" >&2
+		exit 1
+	}
+	exec "${bash}" "${0}" "${@}"
+fi
+
+case "${BASH_VERSION}" in
+[0-3].*|4.[01].*)
+	echo "ptxdist: error: bash >= 4.2 is required, found ${BASH_VERSION} as '${BASH}'" >&2
+	exit 1
+	;;
+esac
+
+# e.g. when started as 'sh' with /bin/sh -> bash
+set +o posix
 
 LANG=C
 LC_ALL=POSIX
diff --git a/bin/ptxdist-auto-version b/bin/ptxdist-auto-version
index 2f6414ae0..92c50fc3d 100755
--- a/bin/ptxdist-auto-version
+++ b/bin/ptxdist-auto-version
@@ -1,7 +1,7 @@
-#!/bin/bash
+#!/bin/sh
 
 #
-# bash implementation of realpath / readlink -f
+# shell implementation of realpath / readlink -f
 #   arg1 - filename
 realpath()
 {
-- 
2.47.3