nixpkgs/pkgs/build-support/setup-hooks/patch-shebangs.sh

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# This setup hook causes the fixup phase to rewrite all script
# interpreter file names (`#! /path') to paths found in $PATH. E.g.,
# /bin/sh will be rewritten to /nix/store/<hash>-some-bash/bin/sh.
# /usr/bin/env gets special treatment so that ".../bin/env python" is
# rewritten to /nix/store/<hash>/bin/python. Interpreters that are
# already in the store are left untouched.
fixupOutputHooks+=('if [ -z "$dontPatchShebangs" -a -e "$prefix" ]; then patchShebangs "$prefix"; fi')
patchShebangs() {
local dir="$1"
header "patching script interpreter paths in $dir"
local f
local oldPath
local newPath
local arg0
local args
local oldInterpreterLine
local newInterpreterLine
find "$dir" -type f -perm -0100 | while read f; do
if [ "$(head -1 "$f" | head -c+2)" != '#!' ]; then
# missing shebang => not a script
continue
fi
oldInterpreterLine=$(head -1 "$f" | tail -c+3)
read -r oldPath arg0 args <<< "$oldInterpreterLine"
if $(echo "$oldPath" | grep -q "/bin/env$"); then
# Check for unsupported 'env' functionality:
# - options: something starting with a '-'
# - environment variables: foo=bar
if $(echo "$arg0" | grep -q -- "^-.*\|.*=.*"); then
echo "unsupported interpreter directive \"$oldInterpreterLine\" (set dontPatchShebangs=1 and handle shebang patching yourself)"
exit 1
fi
newPath="$(command -v "$arg0" || true)"
else
if [ "$oldPath" = "" ]; then
# If no interpreter is specified linux will use /bin/sh. Set
# oldpath="/bin/sh" so that we get /nix/store/.../sh.
oldPath="/bin/sh"
fi
newPath="$(command -v "$(basename "$oldPath")" || true)"
args="$arg0 $args"
fi
# Strip trailing whitespace introduced when no arguments are present
newInterpreterLine=$(echo "$newPath $args" | sed 's/[[:space:]]*$//')
if [ -n "$oldPath" -a "${oldPath:0:${#NIX_STORE}}" != "$NIX_STORE" ]; then
if [ -n "$newPath" -a "$newPath" != "$oldPath" ]; then
echo "$f: interpreter directive changed from \"$oldInterpreterLine\" to \"$newInterpreterLine\""
# escape the escape chars so that sed doesn't interpret them
escapedInterpreterLine=$(echo "$newInterpreterLine" | sed 's|\\|\\\\|g')
sed -i -e "1 s|.*|#\!$escapedInterpreterLine|" "$f"
fi
fi
done
stopNest
}