check_unbalanced_macros.sh: A script to look for unbalanced *roff/man macro pairs

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/scripts/check_unbalanced_macros.sh b/scripts/check_unbalanced_macros.sh
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+#!/bin/bash
+#
+# check_unbalanced_macros.sh
+#
+# Dec 2007, Michael Kerrisk
+#
+# Look for unbalanced pairs of macros in man page source files, with
+# $1 and $2 specifying the macro pair.  These arguments should
+# _not_ include the leading dot (.) in the macro.
+# As output, the program prints the line numbers containing each macro,
+# and if an unbalanced macro is detected, the string "UNBALANCED!"
+# is printed.
+#
+# Example usage:
+#
+#     sh check_unbalanced_macros.sh nf fi */*.[1-8]
+#     sh check_unbalanced_macros.sh RS RE */*.[1-8]
+#     sh check_unbalanced_macros.sh EX EE */*.[1-8]
+#
+######################################################################
+#
+# (C) Copyright 2020, Michael Kerrisk
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details
+# (http://www.gnu.org/licenses/gpl-2.0.html).
+#
+
+if test $# -lt 4; then
+    echo "Usage: $0 opener closer pages..."
+    exit 1
+fi
+
+opener="$1"
+closer="$2"
+shift 2
+
+for f in $@; do
+    if egrep "^\.($opener|$closer)" $f > /dev/null; then
+        echo "================== $f"
+
+        nl -ba $f |
+            awk 'BEGIN { level = 0 }
+
+                 $2 == "'".$opener"'" { level++ }
+
+                 $2 == "'".$opener"'" || $2 == "'".$closer"'" { 
+                     printf "%s %s %d", $1, $2, level
+                     if (level == 0)
+                         print " UNBALANCED!" 
+                     else
+                         print ""
+                 }
+
+                 $2 == "'".$closer"'" { level-- }
+
+                 END { 
+                     if (level != 0) 
+                         print "UNBALANCED!" 
+                 }'
+    fi
+done