use POSIX-compliant syntax

Author: yihui

tools/install-bin-unix.sh

@@ -39,7 +39,7 @@ if [ -z $TINYTEX_VERSION ]; then
   TINYTEX_URL="https://github.com/rstudio/tinytex-releases/releases/download/daily/$TINYTEX_INSTALLER"
 else
   # the installer was accidentally named "install-unix" instead of "installer-unix" before v2025.01
-  if [ "$TINYTEX_INSTALLER" = "installer-unix" ] && [[ "$TINYTEX_VERSION" -le "2025.01" ]]; then
+  if [ "$TINYTEX_INSTALLER" = "installer-unix" ] && [ "$TINYTEX_VERSION" \< "2025.02" ]; then
     TINYTEX_INSTALLER="install-unix"
   fi
   TINYTEX_URL="https://github.com/rstudio/tinytex-releases/releases/download/v$TINYTEX_VERSION/$TINYTEX_INSTALLER-v$TINYTEX_VERSION"
@@ -49,7 +49,7 @@ if [ $OSNAME = 'Darwin' ]; then
     curl -L -f --retry 10 --retry-delay 30 ${TINYTEX_URL}.tgz -o TinyTeX.tgz
     tar xf TinyTeX.tgz -C $(dirname $TEXDIR)
     rm TinyTeX.tgz
-else if [[ "$TINYTEX_INSTALLER" =~ ^"TinyTeX-" ]]; then
+else if [ "${TINYTEX_INSTALLER#"TinyTeX-"}" != "$TINYTEX_INSTALLER" ]; then
     wget --retry-connrefused --progress=dot:giga -O TinyTeX.tar.gz ${TINYTEX_URL}.tar.gz
     tar xf TinyTeX.tar.gz -C $(dirname $TEXDIR)
     rm TinyTeX.tar.gz