Re: Global History Substitution

[Peter Stephenson <pws@csr.com>]

Chris Johnson <cjohnson@cs.utk.edu> wrote:
> Is there a way to do global substitution on the previous command in ^
> notation?  For instance,
> 
>    $ echo a b b b
>    $ ^b^beta^
> 
> yields
> 
>    $ echo a beta b b
> 
> Certainly I could do !!:gs/b/beta.  This isn't near as simple as
> something like gs/b/beta or ^b^beta^g.  Anything I'm missing in the
> manual?

No, I think with this particular feature you're stuck.  It's a historical
oddity that the "g" for global doesn't work as a qualifier, so the ^
notation is restricted.

It turns out that fixing the code to use :g like a qualifier isn't that
difficult, however...  that's ^b^beta^:g, since if the colon is missing the
g is treated like ordinary text.

Index: Doc/Zsh/expn.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/expn.yo,v
retrieving revision 1.57
diff -u -r1.57 expn.yo
--- Doc/Zsh/expn.yo	1 Nov 2005 18:04:25 -0000	1.57
+++ Doc/Zsh/expn.yo	4 Nov 2005 11:05:01 -0000
@@ -117,6 +117,8 @@
 More precisely, the sequence `tt(^)var(foo)tt(^)var(bar)tt(^)' is
 synonymous with `tt(!!:s)tt(^)var(foo)tt(^)var(bar)tt(^)', hence other
 modifiers (see noderef(Modifiers)) may follow the final `tt(^)'.
+In particular, `tt(^)var(foo)tt(^)var(bar)tt(:g)' performs a global
+substitution.
 
 If the shell encounters the character sequence `tt(!")'
 in the input, the history mechanism is temporarily disabled until
@@ -254,10 +256,14 @@
 )
 item(tt(s/)var(l)tt(/)var(r)[tt(/)])(
 Substitute var(r) for var(l) as described below.
-Unless preceded immediately by a tt(g), with no colon between,
-the substitution is done only for the
+The substitution is done only for the
 first string that matches var(l).  For arrays and for filename
 generation, this applies to each word of the expanded text.
+
+The forms `tt(gs/)var(l)tt(/)var(r)' and `tt(s/)var(l)tt(/)var(r)tt(/:g)'
+perform global substitution, i.e. substitute every occurrence of var(r)
+for var(l).  Note that the tt(g) or tt(:g) must appear in exactly the
+position shown.
 )
 item(tt(&))(
 Repeat the previous tt(s) substitution.  Like tt(s), may be preceded
Index: Src/hist.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/hist.c,v
retrieving revision 1.60
diff -u -r1.60 hist.c
--- Src/hist.c	10 Aug 2005 10:56:41 -0000	1.60
+++ Src/hist.c	4 Nov 2005 11:05:02 -0000
@@ -295,13 +295,27 @@
 	hwaddc(ingetc());
 }
 
-/* extract :s/foo/bar/ delimiters and arguments */
+/*
+ * Extract :s/foo/bar/ delimiters and arguments
+ *
+ * The first character expected is the first delimiter.
+ * The arguments are stored in the hsubl and hsubr variables.
+ *
+ * subline is the part of the command line to be matched.
+ *
+ * *gbalp is set to 1 to indicate a trailing ':g', i.e. a
+ * global substitution.
+ *
+ * If a ':' was found but was not followed by a 'g',
+ * *cflagp is set to 1 and the input is backed up to the
+ * character following the colon.
+ */
 
 /**/
 static int
-getsubsargs(char *subline)
+getsubsargs(char *subline, int *gbalp, int *cflagp)
 {
-    int del;
+    int del, follow;
     char *ptr1, *ptr2;
 
     del = ingetc();
@@ -315,6 +329,17 @@
     }
     zsfree(hsubr);
     hsubr = ptr2;
+    follow = ingetc();
+    if (follow == ':') {
+	follow = ingetc();
+	if (follow == 'g')
+	    *gbalp = 1;
+	else {
+	    inungetc(follow);
+	    *cflagp = 1;
+	}
+    } else
+	inungetc(follow);
     if (hsubl && !strstr(subline, hsubl)) {
 	herrflush();
 	zerr("substitution failed", NULL, 0);
@@ -348,14 +373,16 @@
 
     /* look, no goto's */
     if (isfirstch && c == hatchar) {
+	int gbal = 0;
+
 	/* Line begins ^foo^bar */
 	isfirstch = 0;
 	inungetc(hatchar);
 	if (!(ehist = gethist(defev))
 	    || !(sline = getargs(ehist, 0, getargc(ehist)))
-	    || getsubsargs(sline) || !hsubl)
+	    || getsubsargs(sline, &gbal, &cflag) || !hsubl)
 	    return -1;
-	subst(&sline, hsubl, hsubr, 0);
+	subst(&sline, hsubl, hsubr, gbal);
     } else {
 	/* Line doesn't begin ^foo^bar */
 	if (c != ' ')
@@ -577,7 +604,7 @@
 		}
 		break;
 	    case 's':
-		if (getsubsargs(sline))
+		if (getsubsargs(sline, &gbal, &cflag))
 		    return -1; /* fall through */
 	    case '&':
 		if (hsubl && hsubr)

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070


This message has been scanned for viruses by BlackSpider MailControl - www.blackspider.com