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utime undef, undef, @files #712

Closed p5pRT closed 20 years ago

p5pRT commented 24 years ago

Migrated from rt.perl.org#1614 (status was 'resolved')

Searchable as RT1614$

p5pRT commented 24 years ago

From andrew@pimlott.ne.mediaone.net

On Solaris\, and presumably most systems\, the utime(2) system call applies more lenient authorization checks if I only want to set the time to now (by passing a NULL struct utimbuf). But the perl utime function always uses the form that requires me to own the file. I suggest that if the first two arguments to utime are both undef\, perl call the NULL form of utime(2).

Andrew

Perl Info ``` Site configuration information for perl 5.00503: Configured by torin at Wed Sep 22 00:18:38 PDT 1999. Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration: Platform: osname=linux, osvers=2.0.36, archname=i386-linux uname='linux perv 2.0.36 #2 wed nov 18 03:00:48 pst 1998 i686 unknown ' hint=recommended, useposix=true, d_sigaction=define usethreads=undef useperlio=undef d_sfio=undef Compiler: cc='cc', optimize='-O2', gccversion=2.95.1 19990809 (prerelease) cppflags='-Dbool=char -DHAS_BOOL -D_REENTRANT -DDEBIAN -I/usr/local/include' ccflags ='-Dbool=char -DHAS_BOOL -D_REENTRANT -DDEBIAN -I/usr/local/include' stdchar='char', d_stdstdio=undef, usevfork=false intsize=4, longsize=4, ptrsize=4, doublesize=8 d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12 alignbytes=4, usemymalloc=n, prototype=define Linker and Libraries: ld='cc', ldflags =' -L/usr/local/lib' libpth=/usr/local/lib /lib /usr/lib libs=-lnsl -lndbm -lgdbm -ldbm -ldb -ldl -lm -lc -lposix -lcrypt libc=, so=so, useshrplib=false, libperl=libperl.a Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic' cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib' Locally applied patches: @INC for perl 5.00503: /usr/lib/perl5/5.005/i386-linux /usr/lib/perl5/5.005 /usr/local/lib/site_perl/i386-linux /usr/local/lib/site_perl /usr/lib/perl5 . Environment for perl 5.00503: HOME=/home/andrew LANG (unset) LANGUAGE (unset) LD_LIBRARY_PATH (unset) LOGDIR (unset) PATH=/home/andrew/bin:/usr/sbin:/sbin:/home/andrew/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games PERL_BADLANG (unset) SHELL=/usr/bin/zsh ```
p5pRT commented 22 years ago

From @rspier

I've implemented this\, cause it sounds like a good idea. (There are lots of other places where Perl defers to the underlying C library. This is a good place to do it.) This should not break any existing functionality.

Patch below.

The documentation for 'utime(2)' on all the systems I could get my hands on says that this is valid. One\, even says this in a section labeled "STANDARDS".

-R

Inline Patch ```diff --- doio.c.org Sat May 26 18:37:55 2001 +++ doio.c Sat May 26 19:00:48 2001 @@ -1667,20 +1667,31 @@ } utbuf; #endif + SV* accessed = *++mark; + SV* modified = *++mark; + void * utbufp = &utbuf; + + /* be like C, and if both times are undefined, let the C + library figure out what to do. This usually means + "current time" */ + + if ( accessed == &PL_sv_undef && modified == &PL_sv_undef ) + utbufp = NULL; + Zero(&utbuf, sizeof utbuf, char); #ifdef BIG_TIME - utbuf.actime = (Time_t)SvNVx(*++mark); /* time accessed */ - utbuf.modtime = (Time_t)SvNVx(*++mark); /* time modified */ + utbuf.actime = (Time_t)SvNVx(accessed); /* time accessed */ + utbuf.modtime = (Time_t)SvNVx(modified); /* time modified */ #else - utbuf.actime = (Time_t)SvIVx(*++mark); /* time accessed */ - utbuf.modtime = (Time_t)SvIVx(*++mark); /* time modified */ + utbuf.actime = (Time_t)SvIVx(accessed); /* time accessed */ + utbuf.modtime = (Time_t)SvIVx(modified); /* time modified */ #endif APPLY_TAINT_PROPER(); tot = sp - mark; while (++mark <= sp) { char *name = SvPVx(*mark, n_a); APPLY_TAINT_PROPER(); - if (PerlLIO_utime(name, &utbuf)) + if (PerlLIO_utime(name, utbufp)) tot--; } } --- pod/perlfunc.pod.original Sat May 26 10:17:09 2001 +++ pod/perlfunc.pod Sat May 26 19:39:33 2001 @@ -5622,6 +5622,13 @@ $now = time; utime $now, $now, @ARGV; +If the fisrt two two elements of the list are C, then the +system (C Library) utime will be called with a null second argument. +On most machines, this will set the files access and modification time +to the current time. (i.e. equivalent to the example above.) + + utime undef, undef, @ARGV; + =item values HASH Returns a list consisting of all the values of the named hash. (In a ```
p5pRT commented 22 years ago

From [Unknown Contact. See original ticket]

Thanks! Can I suggest​:

+If the fisrt two two elements of the list are C\\, then the +system (C Library) utime will be called with a null second argument. +On most machines\, this will set the files access and modification time +to the current time. (i.e. equivalent to the example above.)

Replace "On most ..." with something like

  This will set the file's access and modification time to the   current time (i.e. equivalent to the example above)\, but (on   most systems) will work on any file you can write to\, not just   files you own.

I think if some system were found to do something else with a null argument\, this should be worked around in perl.

(Even if you don't take my suggestion\, take my apostrophe\, O illustrious porter. Also\, s/fisrt/first/\, s/two two/two/.)

Andrew

p5pRT commented 22 years ago

From @rspier

Thanks! Can I suggest​:

+If the fisrt two two elements of the list are C\\, then the +system (C Library) utime will be called with a null second argument. +On most machines\, this will set the files access and modification time +to the current time. (i.e. equivalent to the example above.)

Replace "On most ..." with something like

This will set the file's access and modification time to the current time (i.e. equivalent to the example above)\, but (on most systems) will work on any file you can write to\, not just files you own.

The ownership rules vary from system to system\, but are generaly the same for both cases. (i.e providing arguments/not providing arguments) Because that is dependent on the actual underlying implementation\, I don't think the perl documentation should mention that.

I think if some system were found to do something else with a null argument\, this should be worked around in perl.

(Even if you don't take my suggestion\, take my apostrophe\, O illustrious porter. Also\, s/fisrt/first/\, s/two two/two/.)

Andrew

New doc patch follows​:

-R

Inline Patch ```diff --- perlfunc.pod.original Sat May 26 10:17:09 2001 +++ perlfunc.pod Sun May 27 00:16:59 2001 @@ -5622,6 +5622,13 @@ $now = time; utime $now, $now, @ARGV; +If the first two elements of the list are C, then the utime(2) +function in the C library will be called with a null second argument. +On most systems, this will set the file's access and modification +times to the current time. (i.e. equivalent to the example above.) + + utime undef, undef, @ARGV; + =item values HASH Returns a list consisting of all the values of the named hash. (In a ```
p5pRT commented 22 years ago

From @rspier

I thought about that\, and it was starting to look real ugly. the t/io/fs.t tests for utime are a small nest of platform varying tests\, and I really didn't want to touch or expand them.

The patch shouldn't change the common case functionality.

-R

p5pRT commented 22 years ago

From @jhi

I believe "rat's nest" is the technical term :-)

and I really didn't want to touch or expand them.

The patch shouldn't change the common case functionality.

True. I'm just afraid that in some far-away platform utime(2) will crash and burn with NULL arguments...

-R