improve shellcheck comments

1985/shapiro/try.alt.sh

@@ -37,9 +37,8 @@ done
 # it either.
 while :; do
     read -r -p "Enter a value (any non-digit = quit): "
-    # ^-- SC2143 (style): Use grep -q instead of comparing output with [ -n .. ].
-    # shellcheck disable=SC2143
-    if [[ $(echo "$REPLY" | grep -E '\<[0-9]+\>') ]]; then
+    GREP_REPLY=$(echo "$REPLY" | grep -E '\<[0-9]+\>')
+    if [[ -z $GREP_REPLY ]]; then
 	make clobber CC="$CC" SIZE="$REPLY" alt >/dev/null
 	./shapiro.alt
     else

1985/sicherman/try.alt.sh

@@ -35,8 +35,8 @@ read -r -n 1 -p "Press any key to run: ./sicherman.alt < sicherman.alt.c | ./sic
 echo 1>&2
 # This warning from ShellCheck is incorrect:
 #
-#   SC2094 (info): Make sure not to read and write the same file in the same pipeline.
-#
+# SC2094 (info): Make sure not to read and write the same file in the same pipeline.
+# https://www.shellcheck.net/wiki/SC2094
 # shellcheck disable=SC2094
 ./sicherman.alt < sicherman.alt.c | ./sicherman.alt | diff -s - sicherman.alt.c
 echo "Now explain any differences." 1>&2

1985/sicherman/try.sh

@@ -36,8 +36,8 @@ echo 1>&2
 
 # This warning from ShellCheck is incorrect:
 #
-#   SC2094 (info): Make sure not to read and write the same file in the same pipeline.
-#
+#SC2094 (info): Make sure not to read and write the same file in the same pipeline.
+# https://www.shellcheck.net/wiki/SC2094
 # shellcheck disable=SC2094
 ./sicherman < sicherman.c | ./sicherman | diff -s - sicherman.c
 echo "Now explain any differences." 1>&2