$ multirust update nightly
multirust: installing toolchain 'nightly'
rustup: gpg available. signatures will be verified
/home/vi/home/rust/prefix/bin/rustup.sh: 1512: [: 1: unexpected operator
rustup: downloading manifest for 'nightly'
^C

$ checkbashisms /home/vi/home/rust/prefix/bin/rustup.sh
possible bashism in /home/vi/home/rust/prefix/bin/rustup.sh line 84 ('command' with option other than -p):
    if command -v gpg2 > /dev/null 2>&1; then
possible bashism in /home/vi/home/rust/prefix/bin/rustup.sh line 88 ('command' with option other than -p):
    if command -v "$gpg_exe" > /dev/null 2>&1; then
possible bashism in /home/vi/home/rust/prefix/bin/rustup.sh line 1388 ('command' with option other than -p):
    if command -v "$sha256sum_cmd" > /dev/null 2>&1; then
possible bashism in /home/vi/home/rust/prefix/bin/rustup.sh line 1390 ('command' with option other than -p):
    elif command -v shasum > /dev/null 2>&1; then
possible bashism in /home/vi/home/rust/prefix/bin/rustup.sh line 1407 ('command' with option other than -p):
    if command -v "$sha256sum_cmd" > /dev/null 2>&1; then
possible bashism in /home/vi/home/rust/prefix/bin/rustup.sh line 1409 ('command' with option other than -p):
    elif command -v shasum > /dev/null 2>&1; then
possible bashism in /home/vi/home/rust/prefix/bin/rustup.sh line 1512 (should be 'b = a'):
            if [ $? == 0 ]; then
possible bashism in /home/vi/home/rust/prefix/bin/rustup.sh line 1787 (read with option other than -r):
    read -p "Continue? (y/N) " _yn < /dev/tty