[6266] double backslashes in $0 before passing to (g)awk

[karl]

Revision: 6266
          http://svn.sv.gnu.org/viewvc/?view=rev&root=texinfo&revision=6266
Author:   karl
Date:     2015-05-14 17:28:43 +0000 (Thu, 14 May 2015)
Log Message:
-----------
double backslashes in $0 before passing to (g)awk

Modified Paths:
--------------
    trunk/ChangeLog
    trunk/texindex/texindex.in

Modified: trunk/ChangeLog
===================================================================
--- trunk/ChangeLog     2015-05-13 00:34:02 UTC (rev 6265)
+++ trunk/ChangeLog     2015-05-14 17:28:43 UTC (rev 6266)
@@ -1,3 +1,9 @@
+2015-05-14  Karl Berry  <address@hidden>
+
+       * texindex/texindex.in (escaped0): double backslashes in $0
+       for passing to awk.
+       Report from Eli on texinfo-devel, 09 May 2015 14:04:37.
+
 2015-05-11  Gavin Smith  <address@hidden>
 
        Pretest 5.9.92.

Modified: trunk/texindex/texindex.in
===================================================================
--- trunk/texindex/texindex.in  2015-05-13 00:34:02 UTC (rev 6265)
+++ trunk/texindex/texindex.in  2015-05-14 17:28:43 UTC (rev 6266)
@@ -97,4 +97,21 @@
   exit 1
 fi
 
-exec $awk_binary -v Invocation_name="$0" -f "$ti_script" -- "$@"
+# Suppose a symlink named a\tb (four chars) is made to this script, and
+# "a\tb" --help
+# is invoked.  We want the output to report the program name as the
+# four chars a, \, t, b, not a, tab, b.
+# 
+# But we pass the value using (g)awk -v, and (g)awk processes arguments
+# to -v for escape sequences, so that by the time the rest of the script
+# sees it, it has a tab in it.
+# 
+# Conclusion: we must double any backslashes before invoking gawk,
+# by running the command: sed 's,\\,\\\\,g'
+# 
+# Sadly, since we have to do this in a shell, we need twice
+# as many backslash characters in the input.  Hope it's portable across
+# shells and seds.
+# 
+escaped0=`echo "$0" | sed 's,\\\\,\\\\\\\\,g'`
+exec $awk_binary -v Invocation_name="$escaped0" -f "$ti_script" -- "$@"