Prepend/append to the members of a list

Prepend/append to the members of a list

[Jörg Sommer]

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Hi,

somewhere I've used

% ls foo bar bla

Then I've left the directory. Later I want to do

% ls !ls*:(s/^/dir/)

But it does not work, because the s/// expression doesn't know ^.

Or another example:

% cp dir/*.[1-9](:t:s+^+/usr/share/man/man?/+:s/$/.gz/) .

How can I make it? Is this possible?

Bye, Jörg.
-- 
Was man mühelos erreichen kann, ist gewöhnlich nicht der Mühe wert,
erreicht zu werden.

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Re: Prepend/append to the members of a list

[Nikolai Weibull]

On 10/30/06, Jörg Sommer <joerg@alea.gnuu.de> wrote:
> Hi,
>
> somewhere I've used
>
> % ls foo bar bla
>
> Then I've left the directory. Later I want to do
>
> % ls !ls*:(s/^/dir/)
>
> But it does not work, because the s/// expression doesn't know ^.

OK, this isn't a very good solution, but it works:

a=(!ls*); ls dir/$a

and it requires that you have rcexpandparam set.

  nikolai

Re: Prepend/append to the members of a list

[Bart Schaefer]

On Oct 30,  6:09pm, Jörg Sommer wrote:
}
} % ls !ls*:(s/^/dir/)
} 
} But it does not work, because the s/// expression doesn't know ^.

Even if history substitution did understand beginning-of-word, that
still wouldn't work.  You'd at the least need :gs and some character
other than slash as the separator.

Usually in this situation I would do something like

% (cd dir; !ls )

Nikolai's suggestion can be tweaked to not require rcexpandparam:

% a=( !ls:* ); ls dir/$^a

Or this:

% ls dir/${^$(echo !{ls:*:q})}

} Or another example:
} 
} % cp dir/*.[1-9](:t:s+^+/usr/share/man/man?/+:s/$/.gz/) .

There you're in a bit of a pickle because you're using history modifiers
on a glob pattern, which is even more limited.  I believe the closest
you'd get without pain [#] is:

% cp /usr/share/man/man?/${^$(echo dir/*.[1-9](:t)}.gz .

which isn't that much uglier than what you constructed.

Of course, if you do this specific thing often you can do

% function mangz { reply=(/usr/share/man/man?/$REPLY:t.gz) }
% cp dir/*.[1-9](+mangz) .

[#] Pain is safely quoting special characters in the file name:

% cp /usr/share/man/man?/${^$(echo dir/*.[1-9](:te.'reply=${(q)REPLY}'.))}.gz .

-- 

Re: Prepend/append to the members of a list

[Peter Stephenson]

=?iso-8859-1?Q?J=F6rg?= Sommer wrote:
> somewhere I've used
> 
> % ls foo bar bla
> 
> Then I've left the directory. Later I want to do
> 
> % ls !ls*:(s/^/dir/)
> 
> But it does not work, because the s/// expression doesn't know ^.
> 
> Or another example:
> 
> % cp dir/*.[1-9](:t:s+^+/usr/share/man/man?/+:s/$/.gz/) .
> 
> How can I make it? Is this possible?

It's not so difficult to add an option HIST_SUBST_PATTERN to allow
pattern matching.  However, it's zsh patterns, not regular expressions,
so (like substitution in parameter matching) you use # for head
and % for tail (and you can combine them as #% to anchor at both ends).

setopt histsubstpattern
ls !ls*:s+#+dir/+

What you wanted didn't need pattern matching, but to avoid
incompatibilities it did need a new option, so I extended it a bit
more generously while I was adding that.  See the documentation
for examples.  As always, tokenization and quoting is a bit hairier than
it deserves to be.

I can't see any good reason to use this in place of ${.../...}
substitution; it works in parameters just to be consistent.

I discovered a couple of bugs:  subst() was returning permanently
allocated strings, but this was only reflected in the caller in one
place, due to the usual doubts about the (undocumented) API.

Also, longest match substitution at the tail didn't handle null strings;
the use of :s/%/.../ showed up this up.  (It's "longest match" because
that's the default behaviour of pattern matches; obviously that shouldn't
affect the result here.)

Index: Completion/compinit
===================================================================
RCS file: /cvsroot/zsh/zsh/Completion/compinit,v
retrieving revision 1.16
diff -u -r1.16 compinit
--- Completion/compinit	28 Jun 2006 13:12:55 -0000	1.16
+++ Completion/compinit	31 Oct 2006 14:35:44 -0000
@@ -128,25 +128,26 @@
 # The standard options set in completion functions.
 
 _comp_options=(
-       extendedglob
        bareglobqual
+       extendedglob
        glob
        multibyte
        nullglob
        rcexpandparam
        unset
-    NO_markdirs
+    NO_allexport
+    NO_aliases
+    NO_cshnullglob
+    NO_errexit
     NO_globsubst
-    NO_shwordsplit
-    NO_shglob
+    NO_histsubstpattern
     NO_kshglob
     NO_ksharrays
     NO_kshtypeset
-    NO_cshnullglob
-    NO_allexport
-    NO_aliases
-    NO_errexit
+    NO_markdirs
     NO_octalzeroes
+    NO_shwordsplit
+    NO_shglob
     NO_warncreateglobal
 )
 
Index: Doc/Zsh/expn.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/expn.yo,v
retrieving revision 1.72
diff -u -r1.72 expn.yo
--- Doc/Zsh/expn.yo	13 Oct 2006 21:49:52 -0000	1.72
+++ Doc/Zsh/expn.yo	31 Oct 2006 14:35:46 -0000
@@ -258,7 +258,8 @@
 Substitute var(r) for var(l) as described below.
 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.
+generation, this applies to each word of the expanded text.  See
+below for further notes on substitutions.
 
 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)
@@ -273,8 +274,8 @@
 )
 enditem()
 
-The tt(s/l/r/) substitution works as follows.  The left-hand side of
-substitutions are not regular expressions, but character strings.  Any
+The tt(s/l/r/) substitution works as follows.  By default the left-hand
+side of substitutions are not patterns, but character strings.  Any
 character can be used as the delimiter in place of `tt(/)'.  A
 backslash quotes the delimiter character.  The character `tt(&)', in
 the right-hand-side var(r), is replaced by the text from the
@@ -286,6 +287,40 @@
 Note the same record of the last var(l) and var(r) is maintained
 across all forms of expansion.
 
+If the option tt(HIST_SUBST_PATTERN) is set, var(l) is treated as
+a pattern of the usual form desribed in
+ifzman(the section FILENAME GENERATION below)\
+ifnzman(noderef(Filename Generation)).  This can be used in
+all the places where modifiers are available; note, however, that
+in globbing qualifiers parameter substitution has already taken place,
+so parameters in the replacement string should be quoted to ensure
+they are replaced at the correct time.
+Note also that complicated patterns used in globbing qualifiers may
+need the extended glob qualifier notation
+tt(LPAR()#q:s/)var(...)tt(/)var(...)tt(/RPAR()) in order for the
+shell to recognize the expression as a glob qualifer.  Further,
+note that bad patterns in the substitution are not subject to
+the tt(NO_BAD_PATTERN) option so will cause an error.
+
+When tt(HIST_SUBST_PATTERN) is set, var(l) may start with a tt(#)
+to indicate that the pattern must match at the start of the string
+to be substituted, and a tt(%) may appear at the start or after an tt(#)
+to indicate that the pattern must match at the end of the string
+to be substituted.
+
+For example, the following piece of filename generation code
+with the tt(EXTENDED_GLOB) option:
+
+example(print *.c+LPAR()#q:s/#%+LPAR()#b+RPAR()s+LPAR()*+RPAR().c/'S${match[1]}.C'/+RPAR())
+
+takes the expansion of tt(*.c) and applies the glob qualifiers in the
+tt(LPAR()#q)var(...)tt(RPAR()) expression, which consists of a substitution
+modifier anchored to the start and end of each word (tt(#%)).  This
+turns on backreferences (tt(LPAR()#b+RPAR())), so that the parenthesised
+subexpression is available in the replacement string as tt(${match[1]}).
+The replacement string is quoted so that the parameter is not substituted
+before the start of filename generation.
+
 The following tt(f), tt(F), tt(w) and tt(W) modifiers work only with
 parameter expansion and filename generation.  They are listed here to
 provide a single point of reference for all modifiers.
Index: Doc/Zsh/options.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/options.yo,v
retrieving revision 1.48
diff -u -r1.48 options.yo
--- Doc/Zsh/options.yo	25 Jul 2006 18:10:38 -0000	1.48
+++ Doc/Zsh/options.yo	31 Oct 2006 14:35:47 -0000
@@ -376,6 +376,15 @@
 filename generation.  Braces (and commas in between) do not become eligible
 for expansion.
 )
+pindex(HIST_SUBST_PATTERN)
+item(tt(HIST_SUBST_PATTERN))(
+Substitutions using the tt(:s) and tt(:&) history modifiers are performed
+with pattern matching instead of string matching.  This occurs wherever
+history modifiers are valid, including glob qualifiers and parameters.
+See
+ifzman(the section Modifiers in zmanref(zshexp))\
+ifnzman(noderef(Modifiers)).
+)
 pindex(IGNORE_BRACES)
 cindex(disabling brace expansion)
 cindex(brace expansion, disabling)
Index: Src/glob.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/glob.c,v
retrieving revision 1.53
diff -u -r1.53 glob.c
--- Src/glob.c	30 Jul 2006 18:00:37 -0000	1.53
+++ Src/glob.c	31 Oct 2006 14:35:50 -0000
@@ -2366,6 +2366,10 @@
 		}
 		umlen -= iincchar(&t);
 	    }
+	    if (pattrylen(p, s + l, 0, 0, ioff)) {
+		*sp = get_match_ret(*sp, l, l, fl, replstr, repllist);
+		return 1;
+	    }
 	    break;
 
 	case SUB_SUBSTR:
@@ -2566,7 +2570,7 @@
 
     /* munge the whole string: no match, so no replstr */
     *sp = get_match_ret(*sp, 0, 0, fl, 0, 0);
-    return 1;
+    return (fl & SUB_RETFAIL) ? 0 : 1;
 }
 
 /**/
Index: Src/hist.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/hist.c,v
retrieving revision 1.65
diff -u -r1.65 hist.c
--- Src/hist.c	28 Jun 2006 13:12:55 -0000	1.65
+++ Src/hist.c	31 Oct 2006 14:35:51 -0000
@@ -323,7 +323,8 @@
     if (strlen(ptr1)) {
 	zsfree(hsubl);
 	hsubl = ptr1;
-    }
+    } else if (!hsubl)		/* fail silently on this */
+	return 0;
     zsfree(hsubr);
     hsubr = ptr2;
     follow = ingetc();
@@ -337,11 +338,6 @@
 	}
     } else
 	inungetc(follow);
-    if (hsubl && !strstr(subline, hsubl)) {
-	herrflush();
-	zerr("substitution failed");
-	return 1;
-    }
     return 0;
 }
 
@@ -354,6 +350,15 @@
     return ehist->nwords ? ehist->nwords-1 : 0;
 }
 
+/**/
+static int
+substfailed(void)
+{
+    herrflush();
+    zerr("substitution failed");
+    return -1;
+}
+
 /* Perform history substitution, returning the next character afterwards. */
 
 /**/
@@ -376,10 +381,15 @@
 	isfirstch = 0;
 	inungetc(hatchar);
 	if (!(ehist = gethist(defev))
-	    || !(sline = getargs(ehist, 0, getargc(ehist)))
-	    || getsubsargs(sline, &gbal, &cflag) || !hsubl)
+	    || !(sline = getargs(ehist, 0, getargc(ehist))))
+	    return -1;
+
+	if (getsubsargs(sline, &gbal, &cflag))
+	    return substfailed();
+	if (!hsubl)
 	    return -1;
-	subst(&sline, hsubl, hsubr, gbal);
+	if (subst(&sline, hsubl, hsubr, gbal))
+	    return substfailed();
     } else {
 	/* Line doesn't begin ^foo^bar */
 	if (c != ' ')
@@ -608,9 +618,10 @@
 		if (getsubsargs(sline, &gbal, &cflag))
 		    return -1; /* fall through */
 	    case '&':
-		if (hsubl && hsubr)
-		    subst(&sline, hsubl, hsubr, gbal);
-		else {
+		if (hsubl && hsubr) {
+		    if (subst(&sline, hsubl, hsubr, gbal))
+			return substfailed();
+		} else {
 		    herrflush();
 		    zerr("no previous substitution");
 		    return -1;
@@ -1629,30 +1640,71 @@
     return str2;
 }
 
+
+/*
+ * Substitute "in" for "out" in "*strptr" and update "*strptr".
+ * If "gbal", do global substitution.
+ *
+ * This returns a result from the heap.  There seems to have
+ * been some confusion on this point.
+ */
+
 /**/
-void
+int
 subst(char **strptr, char *in, char *out, int gbal)
 {
-    char *str = *strptr, *instr = *strptr, *substcut, *sptr, *oldstr;
+    char *str = *strptr, *substcut, *sptr;
     int off, inlen, outlen;
 
     if (!*in)
 	in = str, gbal = 0;
-    if (!(substcut = (char *)strstr(str, in)))
-	return;
-    inlen = strlen(in);
-    sptr = convamps(out, in, inlen);
-    outlen = strlen(sptr);
 
-    do {
-	*substcut = '\0';
-	off = substcut - *strptr + outlen;
-	substcut += inlen;
-	*strptr = tricat(oldstr = *strptr, sptr, substcut);
-	if (oldstr != instr)
-	    zsfree(oldstr);
-	str = (char *)*strptr + off;
-    } while (gbal && (substcut = (char *)strstr(str, in)));
+    if (isset(HISTSUBSTPATTERN)) {
+	int fl = SUB_LONG|SUB_REST|SUB_RETFAIL;
+	char *oldin = in;
+	if (gbal)
+	    fl |= SUB_GLOBAL;
+	if (*in == '#' || *in == Pound) {
+	    /* anchor at head, no flag needed */
+	    in++;
+	}
+	if (*in == '%') {
+	    /* anchor at tail */
+	    in++;
+	    fl |= SUB_END;
+	}
+	if (in == oldin) {
+	    /* no anchor, substring match */
+	    fl |= SUB_SUBSTR;
+	}
+	if (in == str)
+	    in = dupstring(in);
+	if (parse_subst_string(in) || errflag)
+	    return 1;
+	if (parse_subst_string(out) || errflag)
+	    return 1;
+	singsub(&in);
+	if (getmatch(strptr, in, fl, 1, out))
+	    return 0;
+    } else {
+	if ((substcut = (char *)strstr(str, in))) {
+	    inlen = strlen(in);
+	    sptr = convamps(out, in, inlen);
+	    outlen = strlen(sptr);
+
+	    do {
+		*substcut = '\0';
+		off = substcut - *strptr + outlen;
+		substcut += inlen;
+		*strptr = zhtricat(*strptr, sptr, substcut);
+		str = (char *)*strptr + off;
+	    } while (gbal && (substcut = (char *)strstr(str, in)));
+
+	    return 0;
+	}
+    }
+
+    return 1;
 }
 
 /**/
Index: Src/options.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/options.c,v
retrieving revision 1.31
diff -u -r1.31 options.c
--- Src/options.c	22 Aug 2006 09:23:30 -0000	1.31
+++ Src/options.c	31 Oct 2006 14:35:51 -0000
@@ -137,6 +137,7 @@
 {{NULL, "histignorespace",    0},			 HISTIGNORESPACE},
 {{NULL, "histnofunctions",    0},			 HISTNOFUNCTIONS},
 {{NULL, "histnostore",	      0},			 HISTNOSTORE},
+{{NULL, "histsubstpattern",   OPT_EMULATE},              HISTSUBSTPATTERN},
 {{NULL, "histreduceblanks",   0},			 HISTREDUCEBLANKS},
 {{NULL, "histsavebycopy",     OPT_ALL},			 HISTSAVEBYCOPY},
 {{NULL, "histsavenodups",     0},			 HISTSAVENODUPS},
Index: Src/subst.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/subst.c,v
retrieving revision 1.64
diff -u -r1.64 subst.c
--- Src/subst.c	5 Oct 2006 21:53:26 -0000	1.64
+++ Src/subst.c	31 Oct 2006 14:35:52 -0000
@@ -2526,7 +2526,7 @@
             /* This once was executed only `if (qt) ...'. But with that
              * patterns in a expansion resulting from a ${(e)...} aren't
              * tokenized even though this function thinks they are (it thinks
-             * they are because subst_parse_str() turns Qstring tokens
+             * they are because parse_subst_str() turns Qstring tokens
              * into String tokens and for unquoted parameter expansions the
              * lexer normally does tokenize patterns inside parameter
              * expansions). */
@@ -3273,6 +3273,7 @@
 		break;
 
 	    case 's':
+		/* TODO: multibyte delimiter */
 		c = **ptr;
 		(*ptr)++;
 		ptr1 = *ptr;
@@ -3298,7 +3299,8 @@
 		for (tt = hsubl; *tt; tt++)
 		    if (inull(*tt) && *tt != Bnullkeep)
 			chuck(tt--);
-		untokenize(hsubl);
+		if (!isset(HISTSUBSTPATTERN))
+		    untokenize(hsubl);
 		for (tt = hsubr = ztrdup(ptr2); *tt; tt++)
 		    if (inull(*tt) && *tt != Bnullkeep)
 			chuck(tt--);
@@ -3444,15 +3446,8 @@
 		    *str = casemodify(*str, CASMOD_UPPER);
 		    break;
 		case 's':
-		    if (hsubl && hsubr) {
-			char *oldstr = *str;
-
+		    if (hsubl && hsubr)
 			subst(str, hsubl, hsubr, gbal);
-			if (*str != oldstr) {
-			    *str = dupstring(oldstr = *str);
-			    zsfree(oldstr);
-			}
-		    }
 		    break;
 		case 'q':
 		    *str = quotestring(*str, NULL, QT_BACKSLASH);
Index: Src/zsh.h
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/zsh.h,v
retrieving revision 1.101
diff -u -r1.101 zsh.h
--- Src/zsh.h	5 Oct 2006 21:53:27 -0000	1.101
+++ Src/zsh.h	31 Oct 2006 14:35:53 -0000
@@ -1405,6 +1405,7 @@
 #define SUB_ALL		0x0100	/* match complete string */
 #define SUB_GLOBAL	0x0200	/* global substitution ${..//all/these} */
 #define SUB_DOSUBST	0x0400	/* replacement string needs substituting */
+#define SUB_RETFAIL	0x0800  /* return status 0 if no match */
 
 /* Flags as the second argument to prefork */
 #define PF_TYPESET	0x01	/* argument handled like typeset foo=bar */
@@ -1631,6 +1632,7 @@
     HISTREDUCEBLANKS,
     HISTSAVEBYCOPY,
     HISTSAVENODUPS,
+    HISTSUBSTPATTERN,
     HISTVERIFY,
     HUP,
     IGNOREBRACES,
Index: Test/E01options.ztst
===================================================================
RCS file: /cvsroot/zsh/zsh/Test/E01options.ztst,v
retrieving revision 1.16
diff -u -r1.16 E01options.ztst
--- Test/E01options.ztst	23 Sep 2006 06:55:29 -0000	1.16
+++ Test/E01options.ztst	31 Oct 2006 14:35:53 -0000
@@ -487,6 +487,20 @@
 >tmpcd tmpfile1 tmpfile2
 >tmp*
 
+  setopt histsubstpattern
+  print *(:s/t??/TING/)
+  foo=(tmp*)
+  print ${foo:s/??p/THUMP/}
+  foo=(one.c two.c three.c)
+  print ${foo:s/#%(#b)t(*).c/T${match[1]}.X/}
+  print *(#q:s/#(#b)tmp(*e)/'scrunchy${match[1]}'/)
+  unsetopt histsubstpattern
+0:HIST_SUBST_PATTERN option
+>TINGcd TINGfile1 TINGfile2
+>THUMPcd THUMPfile1 THUMPfile2
+>one.c Two.X Three.X
+>scrunchyfile1 scrunchyfile2 tmpcd
+
   setopt ignorebraces
   echo X{a,b}Y
   unsetopt ignorebraces

-- 
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


To access the latest news from CSR copy this link into a web browser:  http://www.csr.com/email_sig.php

Re: Prepend/append to the members of a list

[Bart Schaefer]

On Oct 31,  2:52pm, Peter Stephenson wrote:
}
} +When tt(HIST_SUBST_PATTERN) is set, var(l) may start with a tt(#)
} +to indicate that the pattern must match at the start of the string
} +to be substituted, and a tt(%) may appear at the start or after an tt(#)
} +to indicate that the pattern must match at the end of the string
} +to be substituted.

The doc in parameter expansion says

     The PATTERN may begin with a `#', in which case the PATTERN must
     match at the start of the string, or `%', in which case it must
     match at the end of the string.

Should that doc also say that #% is a legal pattern meaning "anchor
the match at both ends of the string"?

Re: Prepend/append to the members of a list

[Nikolai Weibull]

On 10/31/06, Bart Schaefer <schaefer@brasslantern.com> wrote:
> On Oct 31,  2:52pm, Peter Stephenson wrote:
> }
> } +When tt(HIST_SUBST_PATTERN) is set, var(l) may start with a tt(#)
> } +to indicate that the pattern must match at the start of the string
> } +to be substituted, and a tt(%) may appear at the start or after an tt(#)
> } +to indicate that the pattern must match at the end of the string
> } +to be substituted.
>
> The doc in parameter expansion says
>
>      The PATTERN may begin with a `#', in which case the PATTERN must
>      match at the start of the string, or `%', in which case it must
>      match at the end of the string.
>
> Should that doc also say that #% is a legal pattern meaning "anchor
> the match at both ends of the string"?

So that it matches an empty string you mean?

  nikolai

Re: Prepend/append to the members of a list

[Peter Stephenson]

Bart Schaefer wrote:
> On Oct 31,  2:52pm, Peter Stephenson wrote:
> }
> } +When tt(HIST_SUBST_PATTERN) is set, var(l) may start with a tt(#)
> } +to indicate that the pattern must match at the start of the string
> } +to be substituted, and a tt(%) may appear at the start or after an tt(#)
> } +to indicate that the pattern must match at the end of the string
> } +to be substituted.
> 
> The doc in parameter expansion says
> 
>      The PATTERN may begin with a `#', in which case the PATTERN must
>      match at the start of the string, or `%', in which case it must
>      match at the end of the string.
> 
> Should that doc also say that #% is a legal pattern meaning "anchor
> the match at both ends of the string"?

With the current code, no, because that's not supported.  I
suppose it would be sensible to add that for compatibility---although
it does change the syntax in the not particularly likely but by no means
impossible case that you're substituting a % at the head of a string,
so I'm not so sure.

I didn't add it before because I assumed we already had other ways of
doing it; now I come to think of it, I can't actually think of one that
doesn't involve the use of extended globbing (i.e. (#s) or (#e)).
:# removes a complete match, but doesn't replace it.  None of the
flags that modify matching tell it to force a complete match.  So maybe it
could do with adding.  Any strong views?

However, I screwed up: it doesn't work even for :s/#%.../.../ because
I'd forgotten there was no way to tell the underlying pattern
substitution code to anchor at both ends.  So it accepts the syntax but
actually anchors only at the tail.  That turns out to be easy to fix,
and I'll do it in whatever I commit.

Another annoyance, again to do with the horrors of tokenization when you
do things out of the usual order of parsing, is that you need to quote %
and # with two backslashes.  I'll document this.  It's for basically the
same reason that in glob qualifiers you need an extra layer of quotes
round parameters; I'm not sure I can deal with both problems
consistently and it's probably best to leave this for consistency.

-- 
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


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Re: Prepend/append to the members of a list

[Nikolai Weibull]

On 10/31/06, Nikolai Weibull <now@bitwi.se> wrote:
> On 10/31/06, Bart Schaefer <schaefer@brasslantern.com> wrote:
> > On Oct 31,  2:52pm, Peter Stephenson wrote:
> > }
> > } +When tt(HIST_SUBST_PATTERN) is set, var(l) may start with a tt(#)
> > } +to indicate that the pattern must match at the start of the string
> > } +to be substituted, and a tt(%) may appear at the start or after an tt(#)
> > } +to indicate that the pattern must match at the end of the string
> > } +to be substituted.
> >
> > The doc in parameter expansion says
> >
> >      The PATTERN may begin with a `#', in which case the PATTERN must
> >      match at the start of the string, or `%', in which case it must
> >      match at the end of the string.
> >
> > Should that doc also say that #% is a legal pattern meaning "anchor
> > the match at both ends of the string"?
>
> So that it matches an empty string you mean?

Oops, still in regex mode.  Forget that question.

  nikolai

Re: Prepend/append to the members of a list

[Peter Stephenson]

Peter Stephenson <pws@csr.com> wrote:
> >      The PATTERN may begin with a `#', in which case the PATTERN must
> >      match at the start of the string, or `%', in which case it must
> >      match at the end of the string.
> > 
> > Should that doc also say that #% is a legal pattern meaning "anchor
> > the match at both ends of the string"?
> 
> With the current code, no, because that's not supported.  I
> suppose it would be sensible to add that for compatibility---although
> it does change the syntax in the not particularly likely but by no means
> impossible case that you're substituting a % at the head of a string,
> so I'm not so sure.

I've committed the patch with this change, so ${param/#%foo/bar} does mean
"foo must match the whole element".  There's a note in README about the
change.

-- 
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


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