TOOLS_PLATFORM.sh = /usr/bin/bash is not ksh93, so problems with '/usr/bin/head'

[ghost]

came across a problem that is exacerbated with the shell being now by default /usr/bin/bash.
Namely, 'head' is a ksh93 builtin that accepts '-c chars' whereas bash doesn't have this builtin and uses /usr/bin/head which doesn't. gnu-coreutils in illumos and coreutils in pkgsrc provide 'head' :-=) accepting the '-c char' syntax.

richard@devzone:~$ ksh 'head -c'
head: -c: numeric chars argument expected
Usage: head [-qv] [-n lines] [-c chars] [-s skip] [ file ... ]
richard@devzone:~$ /usr/bin/head -c
/usr/bin/head: illegal option -- c
usage: head [-n #] [-#] [filename...]
richard@devzone:~$ /opt/pkg/gnu/bin/head -c
/opt/pkg/gnu/bin/head : l'option requiert un argument -- « c »
Saisissez « /opt/pkg/gnu/bin/head --help » pour plus d'informations.

in the following example from x11/gnome-themes, the single existing patch does the following:

$NetBSD: patch-aa,v 1.5 2009/05/19 23:54:49 wiz Exp $

http://bugzilla.gnome.org/show_bug.cgi?id=583283

--- common/mkiconlinks.sh.orig  2008-09-22 15:09:10.000000000 +0000
+++ common/mkiconlinks.sh
@@ -16,7 +16,7 @@ read NEXTLINE 
 while [ ! -z "$NEXTLINE" ] ; do

    # Skip lines beginning with '#'
-   if [ ! "${NEXTLINE:0:1}" == '#' ]; then
+   if [ ! X"`echo ${NEXTLINE} | head -c 1`" = X'#' ]; then
        #Extract first field, minus its trailing colon
        ORIG_FILE=`echo $NEXTLINE | awk '/:/{print $1}' | sed -e 's/://'`

oddly enough, the reference to the bugzilla report is named:
Bug 583283 - Shell portability in common/mkiconlinks.sh
and this patch is, unfortunately, not portable to solaris with /usr/bin/bash shell.

To be ultimately portable, perhaps this patch should be
if [ ! X"echo ${NEXTLINE} | cut -c 1" = X'#' ]; then

but perhaps this is overkill. Is there an appropriate way to substitute head via PKG_TOOLS.head=/opt/pkg/gnu/bin/head ?

Thanks in advance for advice.

[updated to presume there is only one line of text in NEXTLINE, therefore only changing head to cut should be necessary]

[ghost]

richard@devzone:~/src/pkgsrc/x11/gnome-themes$ git diff --staged .
diff --git a/x11/gnome-themes/distinfo b/x11/gnome-themes/distinfo
index 9749356..d768361 100644
--- a/x11/gnome-themes/distinfo
+++ b/x11/gnome-themes/distinfo
@@ -3,4 +3,4 @@ $NetBSD: distinfo,v 1.37 2010/11/26 11:31:31 drochner Exp $
 SHA1 (gnome-themes-2.32.1.tar.bz2) = 0af9ac28c7b1f7fdd543b3629d9b4711c7412195
 RMD160 (gnome-themes-2.32.1.tar.bz2) = f6fc96686e6076995f0c2a5b25c655e513435941
 Size (gnome-themes-2.32.1.tar.bz2) = 2683723 bytes
-SHA1 (patch-aa) = 10878efeb024f6ef4fde6e0afcad0aabbfa176d1
+SHA1 (patch-aa) = 2e801aacdcaac5b86bdf89c8486e534ad1f06119
diff --git a/x11/gnome-themes/patches/patch-aa b/x11/gnome-themes/patches/patch-aa
index bcfa7a6..9134294 100644
--- a/x11/gnome-themes/patches/patch-aa
+++ b/x11/gnome-themes/patches/patch-aa
@@ -9,7 +9,7 @@ http://bugzilla.gnome.org/show_bug.cgi?id=583283

        # Skip lines beginning with '#'
 -      if [ ! "${NEXTLINE:0:1}" == '#' ]; then
-+      if [ ! X"`echo ${NEXTLINE} | head -c 1`" = X'#' ]; then
++      if [ ! X"`echo ${NEXTLINE} | cut -c 1`" = X'#' ]; then
                #Extract first field, minus its trailing colon
                ORIG_FILE=`echo $NEXTLINE | awk '/:/{print $1}' | sed -e 's/://'`

[jperkin]

Fixed, thanks.