2012/9/5 David Korn <d...@research.att.com>:
[CC:ing ast-developers@research.att.com so that the patch gets archived]
> cc: g...@research.att.com olga.kryzhanov...@gmail.com
> Subject: Re: New syntax for paths relative to directory fds
> (~{dirfd}/foo/bar.txt) ...
>> [Mostly Olga's idea (who is away and can't post anyway here since the
>> AT&T spam filters have a grudge against her native name... ;-( )]
>>
>> Woud the following syntax for paths relative to a directory fd "dirfd"
>> be possible without violating POSIX (right now the only way to archive
>> this is to use /dev/fd/${dirfd}/ ... which works OK but may not be
>> suiteable for a new version of the POSIX standard since POSIX does not
>> mandate any absolute paths):
>>
>> ~{dirfd}/foo/bar/txt
>>
>> (where "dirfd" is a directory fd and "foo/bar/txt" is a path relative
>> to this fd)
>>
>> Example usage:
>> -- snip --
>> # print contents of /etc/profile and /etc/ksh.kshrc
>> redirect {dirfd}<"/etc"
>> cat <~{dirfd}/profile
>> cat <~{dirfd}/ksh.kshrc
>> -- snip --
>>
>
> That could be done. The code is in sh/macro.c sh_tilde_expand2().
[snip]
Attached (as "astksh_tilde_fd001.diff.txt") is a prototype patch.
Technically it works without problems... but I'm not happy with the
|static| variable |devfdname| (short: Ugly |static| variable... which
means: Global variable (with function-local scope). Not thread-safe).
Question: Is it _valid_ to allocate space from |shp->stk| and return
the string as return value of |sh_tilde()| ? Who or what is going to
deallocate the memory chunk ?
----
Bye,
Roland
--
__ . . __
(o.\ \/ /.o) roland.ma...@nrubsig.org
\__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer
/O /==\ O\ TEL +49 641 3992797
(;O/ \/ \O;)
diff -r -u build_i386_64bit_debug/src/cmd/ksh93/sh/macro.c
build_fdsyntax/src/cmd/ksh93/sh/macro.c
--- src/cmd/ksh93/sh/macro.c 2012-08-30 22:33:50.000000000 +0200
+++ src/cmd/ksh93/sh/macro.c 2012-09-05 20:13:46.056881468 +0200
@@ -2679,6 +2679,56 @@
cp = nv_getval(sh_scoped(shp,OLDPWDNOD));
return(cp);
}
+ if(c=='{')
+ {
+ static char devfdname[32+8];
+ char fdnamebuf[PATH_MAX];
+ int fd;
+ const char *s;
+ char *f;
+
+ for(s=&string[1], f=fdnamebuf ;
+ (*s!='\0') && (*s!='}') &&
(s<(string+sizeof(fdnamebuf)-1)) ;
+ s++, f++)
+ *f=*s;
+ *f='\0';
+
+ if (*s != '}')
+ return(NIL(char*));
+
+ /* We assume that variable names cannot start with a digit */
+ if (isdigit(fdnamebuf[0]))
+ {
+ errno=0;
+ fd=strtol(fdnamebuf, (char **)NULL, 10);
+ if(errno!=0)
+ return(NIL(char*));
+ }
+ else
+ {
+ Namval_t *np;
+ np = nv_open(fdnamebuf, shp->var_tree,
NV_VARNAME|NV_NOFAIL|NV_NOADD);
+ if (!np)
+ return(NIL(char*));
+ fd = (int)nv_getnum(np);
+ nv_close(np);
+ }
+
+ if (fd < 0)
+ return(NIL(char*));
+
+ /*
+ * We explicitly convert from string to integer and
+ * back to ensure that nooone can do any stunts to
+ * bypass security
+ */
+#ifdef __SunOS
+ snprintf(devfdname, sizeof(devfdname), "/proc/self/fd/%d/", fd);
+#else
+ snprintf(devfdname, sizeof(devfdname), "/dev/fd/%d/", fd);
+#endif
+ return (devfdname);
+ }
#if _WINIX
if(fcgetc(c)=='/')
{
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