+
+Please use only Bourne shell and bare-bones POSIX program constructs
+in the test scripts. In particular:
+
+- Use `` instead of $().
+
+- Wrap shell variables with "" if they could possibly contain
+ whitespace or special characters that would affect syntax.
+
+- Use the arith_eval() function in common.sh instead of $(()) or expr.
+ It detects at run time if $(()) is available.
+
+- Use grep >/dev/null instead of grep -q.
+
+- Don't use egrep, grep -E, fgrep, grep -F, or other non-portable grep
+ functionality. The built-in case statement supports alternation (|).
+
+- Don't use ! to negate conditions. Instead, use something like:
+ <condition> || <statement>
+ or
+ if <condition>; then :; else <statements> fi
+
+- Separate variable assignment from export (don't assign in export
+ statements).
+
+- Use sed >tmpfile and mv instead of sed -i.
+
+- Avoid depending on the exact format of output from system (non-nmh)
+ programs.
+
+The Heirloom Bourne Shell, http://heirloom.sourceforge.net/sh.html,
+catches many non-portable shell constructs, such as $(), $(()), !, and
+assignment in export statements.
+
+checkbashisms, available at http://sourceforge.net/projects/checkbaskisms/,
+might help some catch problems. Though it misses all of the troublesome
+constructs, except for assignment in an export statement, listed above.