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Re: globbing in conditional expressions
Bart Schaefer wrote on Thu, May 15, 2014 at 07:50:03 -0700:
> On May 15, 9:29am, Daniel Shahaf wrote:
> } Subject: Re: globbing in conditional expressions
> }
> } Bart Schaefer wrote on Wed, May 14, 2014 at 00:18:19 -0700:
> } > Do I read correctly that "shortcircuit" also means "don't return any
> } > file names, just return an indication of whether there is such a file"
> } > ?? (Since you don't allocate the matchbuf array when shortcircuit.)
> }
> } Of course. As soon as you find a single matching filename you return to
> } the caller, so there are two options: either return just a boolean, or
> } return the first matching filename in readdir() order (via $REPLY, as in
> } Roman's post). I'm not sure how idiomatic it would be for a [[ -x ]]
> } condition to set $REPLY.
>
> I would not suggest that [[ -m ... ]] set $REPLY, but why does -m have
> to be the only place where short-circuiting occurs? I could imagine
> adding a globbing flag (#X) [where I'm using X as a placeholder rather
> than a suggestion for the actual flag] which means that the glob returns
> only the first matching file it stumbles upon.
>
> In fact if you had that flag you wouldn't need -m as a condition op, it
> would suffice to do [ ! -z pat(NX) ]. The implementation also would not
> need to change the call signatures of any of the C functions ...
That turned out to be much less code to implement. It's attached, if
anyone finds it useful.
I couldn't get it to work via [ -z ], but this works:
% Src/zsh -fc '() { (( $#@ )) } *(NY); echo $?'
0
% Src/zsh -fc '() { (( $#@ )) } *foobar(NY); echo $?'
1
From 23eafe9265691c0ea6d705100c1ee9e84850efa5 Mon Sep 17 00:00:00 2001
From: Daniel Shahaf <d.s@xxxxxxxxxxxxxxxxxx>
Date: Tue, 13 May 2014 10:18:56 +0000
Subject: [PATCH] Add (Y) glob qualifier that short-circuits.
---
Doc/Zsh/expn.yo | 4 ++++
Src/glob.c | 35 ++++++++++++++++++++++++-----------
Test/D02glob.ztst | 11 +++++++++++
3 files changed, 39 insertions(+), 11 deletions(-)
diff --git a/Doc/Zsh/expn.yo b/Doc/Zsh/expn.yo
index de0f454..65374e8 100644
--- a/Doc/Zsh/expn.yo
+++ b/Doc/Zsh/expn.yo
@@ -2560,6 +2560,10 @@ item(tt(n))(
sets the tt(NUMERIC_GLOB_SORT) option for the current pattern
pindex(NUMERIC_GLOB_SORT, setting in pattern)
)
+item(tt(Y))(
+enables short-circuit mode: the pattern will expand to just the first
+matching filename, if any.
+)
item(tt(o)var(c))(
specifies how the names of the files should be sorted. If var(c) is
tt(n) they are sorted by name (the default); if it is tt(L) they
diff --git a/Src/glob.c b/Src/glob.c
index 07dd7c2..eafb702 100644
--- a/Src/glob.c
+++ b/Src/glob.c
@@ -452,8 +452,8 @@ insert(char *s, int checked)
* tried all of it. */
/**/
-static void
-scanner(Complist q)
+static int
+scanner(Complist q, int shortcircuit)
{
Patprog p;
int closure;
@@ -463,14 +463,15 @@ scanner(Complist q)
init_dirsav(&ds);
if (!q)
- return;
+ return -1;
if ((closure = q->closure)) {
/* (foo/)# - match zero or more dirs */
if (q->closure == 2) /* (foo/)## - match one or more dirs */
q->closure = 1;
else
- scanner(q->next);
+ if (scanner(q->next, shortcircuit) == 1)
+ return 1;
}
p = q->pat;
/* Now the actual matching for the current path section. */
@@ -485,13 +486,13 @@ scanner(Complist q)
int err;
if (l >= PATH_MAX)
- return;
+ return -1;
err = lchdir(pathbuf + pathbufcwd, &ds, 0);
if (err == -1)
- return;
+ return -1;
if (err) {
zerr("current directory lost during glob");
- return;
+ return -1;
}
pathbufcwd = pathpos;
}
@@ -516,7 +517,8 @@ scanner(Complist q)
if (add) {
addpath(str, l);
if (!closure || !statfullpath("", NULL, 1))
- scanner((q->closure) ? q : q->next);
+ if (scanner((q->closure) ? q : q->next, shortcircuit) == 1)
+ return 1;
pathbuf[pathpos = oppos] = '\0';
}
}
@@ -524,6 +526,8 @@ scanner(Complist q)
if (str[l])
str = dupstrpfx(str, l);
insert(str, 0);
+ if (shortcircuit)
+ return 1;
}
} else {
/* Do pattern matching on current path section. */
@@ -534,7 +538,7 @@ scanner(Complist q)
int subdirlen = 0;
if (lock == NULL)
- return;
+ return -1;
while ((fn = zreaddir(lock, 1)) && !errflag) {
/* prefix and suffix are zle trickery */
if (!dirs && !colonmod &&
@@ -614,6 +618,8 @@ scanner(Complist q)
} else
/* if the last filename component, just add it */
insert(fn, 1);
+ if (shortcircuit)
+ return 1;
}
}
closedir(lock);
@@ -626,7 +632,8 @@ scanner(Complist q)
fn += l + 1;
memcpy((char *)&errsfound, fn, sizeof(int));
fn += sizeof(int);
- scanner((q->closure) ? q : q->next); /* scan next level */
+ if (scanner((q->closure) ? q : q->next, shortcircuit) == 1) /* scan next level */
+ return 1;
pathbuf[pathpos = oppos] = '\0';
}
hrealloc(subdirs, subdirlen, 0);
@@ -640,6 +647,7 @@ scanner(Complist q)
close(ds.dirfd);
pathbufcwd = pbcwdsav;
}
+ return 0;
}
/* This function tokenizes a zsh glob pattern */
@@ -1080,6 +1088,7 @@ zglob(LinkList list, LinkNode np, int nountok)
/* and index+1 of the last match */
struct globdata saved; /* saved glob state */
int nobareglob = !isset(BAREGLOBQUAL);
+ int shortcircuit = 0;
if (unset(GLOBOPT) || !haswilds(ostr) || unset(EXECOPT)) {
if (!nountok)
@@ -1461,6 +1470,10 @@ zglob(LinkList list, LinkNode np, int nountok)
/* Numeric glob sort */
gf_numsort = !(sense & 1);
break;
+ case 'Y':
+ /* Short circuit: just check if there are any matches */
+ shortcircuit = !(sense & 1);
+ break;
case 'a':
/* Access time in given range */
g_amc = 0;
@@ -1729,7 +1742,7 @@ zglob(LinkList list, LinkNode np, int nountok)
/* The actual processing takes place here: matches go into *
* matchbuf. This is the only top-level call to scanner(). */
- scanner(q);
+ scanner(q, shortcircuit);
/* Deal with failures to match depending on options */
if (matchct)
diff --git a/Test/D02glob.ztst b/Test/D02glob.ztst
index 1f8f652..0ff088a 100644
--- a/Test/D02glob.ztst
+++ b/Test/D02glob.ztst
@@ -431,6 +431,7 @@
mkdir glob.tmp/dir5
touch glob.tmp/dir5/N123
print glob.tmp/dir5/N<->(N)
+ rm -rf glob.tmp/dir5
0:Numeric glob is not usurped by process substitution.
>glob.tmp/dir5/N123
@@ -526,3 +527,13 @@
>+bus+bus matches +(+bus|-car)
>@sinhats matches @(@sinhats|wrensinfens)
>!kerror matches !(!somethingelse)
+
+ (){ print $#@ } glob.tmp/dir*(Y)
+ (){ print $#@ } glob.tmp/file*(NY)
+ (){ [[ $1 = glob.tmp/dir? ]] && echo "(Y) returns a matching filename" } glob.tmp/dir*(Y)
+ (){ print $@:t } glob.tmp/dir*(Y^Y)
+0:short-circuit modifier
+>1
+>0
+>(Y) returns a matching filename
+>dir1 dir2 dir3 dir4
--
1.7.10.4
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