Index: configure
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/bin/sh
 
 CONFIG="config.mk"
 PREFIX="/usr/local"
@@ -8,7 +8,7 @@
 SSE=auto
 OPENMP=
 LIBPNG_DIR=.
-if [[ "$OSTYPE" =~ "darwin" ]]; then
+if echo "$OSTYPE" | grep -q "darwin"; then
     COCOA_READER=auto
     LCMS2=0
 else
@@ -38,7 +38,7 @@
         echo
         help "--with-openmp=static          compile with multicore support"
         help "--with-lcms2/--without-lcms2  compile with color profile support"
-if [[ "$OSTYPE" =~ "darwin" ]]; then
+if echo "$OSTYPE" | grep -q "darwin"; then
         help "--with-cocoa/--without-cocoa  use Cocoa framework to read images"
         help "--with-libpng=<dir>           search for libpng in directory"
 fi
@@ -110,7 +110,7 @@
 
 # If someone runs sudo make install as very first command, and configure later,
 # $CONFIG cannot be overwritten, and must be deleted before continuing.
-if [[ -f "$CONFIG" && ! -w "$CONFIG" ]]; then
+if [ -f "$CONFIG" -a ! -w "$CONFIG" ]; then
     echo "Cannot overwrite file $CONFIG! Please delete it."
     exit 1
 fi
@@ -147,7 +147,7 @@
 
 find_pkgconfig() {
     LIBNAME=$1
-    if pkg-config --exists "$LIBNAME" &> /dev/null; then
+    if pkg-config --exists "$LIBNAME" >/dev/null 2>&1; then
         cflags "$(pkg-config --cflags "$LIBNAME")"
         lflags "$(pkg-config --libs "$LIBNAME")"
         status "$LIBNAME" "shared ($(pkg-config --modversion "$LIBNAME"))"
@@ -191,11 +191,16 @@
         return 0
     fi
 
-    for i in "${DIRS[@]}"; do
-        DIR=($i)
-        HPATH=$(find_h "${DIR[0]}" "$HEADERPATTERN")
+    # destroys positional parameters
+    set -- ${DIRS}
+    while [ -n "$1" -a -n "$2" ]; do
+        DIRS_h="$1"
+        DIRS_l="$2"
+        shift 2
+
+        HPATH=$(find_h "${DIRS_h}" "$HEADERPATTERN")
         if [ -n "$HPATH" ]; then
-            SOPATH=$(find_f "${DIR[1]}" "$DYNAMICPATTERN")
+            SOPATH=$(find_f "${DIRS_l}" "$DYNAMICPATTERN")
             if [ -n "$SOPATH" ]; then
                 cflags "-I${HPATH%/*}"
                 lflags "-L${SOPATH%/*} -l$DYNAMICLIBNAME"
@@ -250,10 +255,8 @@
 
 # SSE
 if [ "$SSE" = 'auto' ]; then
-    if [[ "$(uname -m)" =~ (amd|x86_)64 ||
-          "$(grep -E -m1 "^flags" /proc/cpuinfo)" =~ "sse" ]]; then
-        SSE=1
-    fi
+    echo $(uname -m) | grep -E -q '(amd|x86_)64' && SSE=1
+    grep -E -m1 -q '^flags.*sse' /proc/cpuinfo 2>/dev/null && SSE=1
 fi
 
 if [ "$SSE" -eq 1 ]; then
@@ -276,9 +279,8 @@
     else
         OPENMPFLAGS="-fopenmp"
     fi
-    if [[ "$("$CC" -xc -E $OPENMPFLAGS <(echo "#ifdef _OPENMP
-           #include <omp.h>
-           #endif") 2>&1)" =~ "omp_get_thread_num" ]]; then
+    if echo "$(printf '#ifdef _OPENMP\n#include <omp.h>\n#endif\n' | \
+        "$CC" -xc -E $OPENMPFLAGS - 2>&1)" | grep -q omp_get_thread_num; then
         cflags "$OPENMPFLAGS"
         lflags "$OPENMPFLAGS"
         status "OpenMP" "yes"
@@ -293,11 +295,13 @@
 fi
 
 # Cocoa
-if [[ "$OSTYPE" =~ "darwin" ]]; then
+if echo "$OSTYPE" | grep -q "darwin"; then
     cflags "-mmacosx-version-min=10.6"
     lflags "-mmacosx-version-min=10.6"
 
-    if [ "$COCOA_READER" != 0 ] && "$CC" 2>/dev/null 1>/dev/null -xc -E <(echo "#import <Cocoa/Cocoa.h>"); then
+    if [ "$COCOA_READER" != 0 ] && \
+        echo "#import <Cocoa/Cocoa.h>" | \
+		"$CC" 2>/dev/null 1>/dev/null -xc -E -; then
         COCOA_READER=1
         cflags "-DUSE_COCOA=1"
         lflags "-framework Cocoa"
@@ -308,19 +312,18 @@
 fi
 
 # pairs of possible *.h and lib*.so locations
-DIRS=("/usr/local/include /usr/local/lib"
-      "/usr/include /usr/lib"
-      "/opt/local/include /opt/local/lib" # macports
-      )
+DIRS="${PREFIX}/include ${PREFIX}/lib \
+      /usr/include /usr/lib \
+      /opt/local/include /opt/local/lib" # macports
 
-if [[ "$OSTYPE" =~ "darwin" ]]; then
+if echo "$OSTYPE" | grep -q "darwin"; then
     SOLIBSUFFIX=dylib
 
     # Search Developer SDK paths, since Apple seems to have dropped the standard Unixy ones
     XCODE_CMD="xcode-select"
     XCODE_PATH=$($XCODE_CMD -p)
-    DIRS+=("$XCODE_PATH/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include $XCODE_PATH/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/lib")
-    DIRS+=("$XCODE_PATH/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/usr/include $XCODE_PATH/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/usr/lib")
+    DIRS="$DIRS $XCODE_PATH/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include $XCODE_PATH/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/lib"
+    DIRS="$DIRS $XCODE_PATH/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/usr/include $XCODE_PATH/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/usr/lib"
 else
     SOLIBSUFFIX=so
 fi
@@ -332,7 +335,7 @@
 if echo "#include \"png.h\"
     int main(){
     return !png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
-}" | "$CC" -xc -std=c99 -o /dev/null $CFLAGS $LDFLAGS - &> /dev/null; then
+}" | "$CC" -xc -std=c99 -o /dev/null $CFLAGS $LDFLAGS - >/dev/null 2>&1; then
     status "libpng" "custom flags"
     SUCCESS=1
 fi
@@ -343,7 +346,7 @@
     if [ -n "$PNGH" ]; then
         PNGH_STRING=$(pngh_string "$PNGH")
         PNGH_MAJMIN=$(pngh_majmin "$PNGH")
-        if [[ -n "$PNGH_STRING" && -n "$PNGH_MAJMIN" ]]; then
+        if [ -n "$PNGH_STRING" -a -n "$PNGH_MAJMIN" ]; then
             LIBPNGA=$(find_f "$LIBPNG_DIR" "libpng${PNGH_MAJMIN}.a")
             if [ -n "$LIBPNGA" ]; then
                 cflags "-I${PNGH%/*}"
@@ -359,14 +362,19 @@
     if find_pkgconfig libpng; then
         SUCCESS=1
     else
-        for i in "${DIRS[@]}"; do
-            DIR=($i)
-            PNGH=$(find_h "${DIR[0]}" "png.h")
+        # destroys positional parameters
+        set -- ${DIRS}
+        while [ -n "$1" -a -n "$2" ]; do
+            DIRS_h="$1"
+            DIRS_l="$2"
+            shift 2
+
+            PNGH=$(find_h "${DIRS_h}" "png.h")
             if [ -n "$PNGH" ]; then
                 PNGH_STRING=$(pngh_string "$PNGH")
                 PNGH_MAJMIN=$(pngh_majmin "$PNGH")
-                if [[ -n "$PNGH_STRING" && -n "$PNGH_MAJMIN" ]]; then
-                    LIBPNGSO=$(find_f "${DIR[1]}" "libpng${PNGH_MAJMIN}.$SOLIBSUFFIX*")
+                if [ -n "$PNGH_STRING" -a -n "$PNGH_MAJMIN" ]; then
+                    LIBPNGSO=$(find_f "${DIRS_l}" "libpng${PNGH_MAJMIN}.$SOLIBSUFFIX*")
                     if [ -n "$LIBPNGSO" ]; then
                         cflags "-I${PNGH%/*}"
                         lflags "-L${LIBPNGSO%/*} -lpng${PNGH_MAJMIN}"
@@ -380,7 +388,7 @@
     fi
 fi
 if [ "$SUCCESS" -eq 0 ]; then
-    if [[ "$OSTYPE" =~ "darwin" ]]; then
+    if echo "$OSTYPE" | grep -q "darwin"; then
         LIBPNG_CMD='`brew install libpng`'
     else
         LIBPNG_CMD='`apt-get install libpng-dev` or `yum install libpng-devel`'