-e on symlink doesn't always succeed?

p5pRT commented 24 years ago

Migrated from rt.perl.org#1211 (status was 'resolved')

Searchable as RT1211$

p5pRT commented 24 years ago

From @vlbrown

Try this little script:

#!/usr/bin/perl
`touch ./foo`; symlink ("./foo"\, "./foolink"); print `ls -l ./foo ./foolink`;
if (-e "./foo") { print "1: file ./foo exists\n"; } if (-l "./foo") { print "1: file ./foo is a link\n"; } if (-e "./foolink") { print "1: file ./foolink exists\n"; } if (-l "./foolink") { print "1: file ./foolink is a link\n"; }
`touch tmp/foo`; symlink ("tmp/foo"\, "tmp/foolink"); print `ls -l tmp/foo tmp/foolink`;
if (-e "tmp/foo") { print "2: file tmp/foo exists\n"; } if (-l "tmp/foo") { print "2: file tmp/foo is a link\n"; } if (-e "tmp/foolink") { print "2: file tmp/foolink exists\n"; } if (-l "tmp/foolink") { print "2: file tmp/foolink is a link\n"; } This prints:

-rw-rw-r-- 1 vlb noodle 0 Aug 12 17:16 ./foo lrwxrwxrwx 1 vlb noodle 3 Aug 12 16:53 ./foolink -> foo 1: file ./foo exists 1: file ./foolink exists 1: file ./foolink is a link -rw-rw-r-- 1 vlb noodle 0 Aug 12 17:16 tmp/foo lrwxrwxrwx 1 vlb noodle 7 Aug 12 17:04 tmp/foolink -> tmp/foo 2: file tmp/foo exists 2: file tmp/foolink is a link

I should see 2: file tmp/foolink exists

When I use if (-e "symlink") or if (-e "./symlink") and "symlink" is a symbolic link\, I get success

When I try to test a path\, such as if (-e "tmp/symlink") I get failure. However if (-l "tmp/symlink") succeeds.

If -l returns success\, then the file (a link) must also exist; but under certain circumstances\, -e fails.

Perl Info

``` Site configuration information for perl 5.00502: Configured by rdm at Sun Feb 7 16:25:31 PST 1999. Summary of my perl5 (5.0 patchlevel 5 subversion 2) configuration: Platform: osname=freebsd, osvers=2.2.8-release, archname=i386-freebsd uname='freebsd cfcl.com 2.2.8-release freebsd 2.2.8-release #0: fri jan 15 18:39:18 pst 1999 rdm@cfcl.com:usrsrcsyscompilefreebie i386 ' hint=recommended, useposix=true, d_sigaction=define usethreads=undef useperlio=undef d_sfio=undef Compiler: cc='cc', optimize='-O', gccversion=2.7.2.1 cppflags='-I/usr/local/include' ccflags ='-I/usr/local/include' stdchar='char', d_stdstdio=undef, usevfork=true 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='ld', ldflags =' -L/usr/local/lib' libpth=/usr/local/lib /usr/lib libs=-ldb -lm -lc -lcrypt libc=/usr/lib/libc.so.3.1, so=so, useshrplib=false, libperl=libperl.a Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags=' ' cccdlflags='-DPIC -fpic', lddlflags='-Bshareable -L/usr/local/lib' Locally applied patches: @INC for perl 5.00502: /usr/local/lib/perl5/5.00502/i386-freebsd /usr/local/lib/perl5/5.00502 /usr/local/lib/perl5/site_perl/5.005/i386-freebsd /usr/local/lib/perl5/site_perl/5.005 . Environment for perl 5.00502: HOME=/home/vlb LANG (unset) LD_LIBRARY_PATH (unset) LOGDIR (unset) PATH=/home/vlb/bin:/usr/local/bin:/usr/local/nib:/usr/bin:/bin:/etc:/sbin:/usr/sbin:/usr/local/games:/usr/games:.:/home/rdm/bin:/home/vlb/projex/ptf/bin PERL_BADLANG (unset) SHELL=/ulb/tcsh ```

p5pRT commented 24 years ago

From @mjdominus

\-rw\-rw\-r\-\-  1 vlb  noodle  0 Aug 12 17&#8203;:16 tmp/foo
lrwxrwxrwx  1 vlb  noodle  7 Aug 12 17&#8203;:04 tmp/foolink \-> tmp/foo
2&#8203;: file tmp/foo exists
2&#8203;: file tmp/foolink is a link

I should see 2: file tmp/foolink exists

The bug is in you\, not in Perl. Try

cat tmp/foolink

and your OS will tell you the same thing:

plover% ls -l tmp/* -rw-r--r-- 1 mjd users 0 Aug 12 20:53 tmp/foo lrwxrwxrwx 1 mjd users 7 Aug 12 20:53 tmp/foolink -> tmp/foo plover:/tmp/vbd% cat tmp/foo plover:/tmp/vbd% cat tmp/foolink cat: tmp/foolink: No such file or directory

That is because tmp/foolink here refers to the nonexistent file tmp/tmp/foo.

If -l returns success\, then the file (a link) must also exist; but under certain circumstances\, -e fails.

-e tests the existence of the *file that is linked to*\, not the existence of the link itself. Thus -e on a dangling symlink will return false.

p5pRT commented 24 years ago

From @vanstyn

In \199908130018\.RAA08993@cfcl\.com\, Vicki Brown writes: :This prints: : : -rw-rw-r-- 1 vlb noodle 0 Aug 12 17:16 ./foo : lrwxrwxrwx 1 vlb noodle 3 Aug 12 16:53 ./foolink -> foo : 1: file ./foo exists : 1: file ./foolink exists : 1: file ./foolink is a link : -rw-rw-r-- 1 vlb noodle 0 Aug 12 17:16 tmp/foo : lrwxrwxrwx 1 vlb noodle 7 Aug 12 17:04 tmp/foolink -> tmp/foo : 2: file tmp/foo exists : 2: file tmp/foolink is a link

That should be 'tmp/foolink -> foo'. The symlink works relative to foolink\, not relative to your current directory.

Note that you can check for the existence of the symlink itself with: lstat "tmp/foolink"; if (-e _) { print "tmp/foolink exists\n"; }

Hugo

p5pRT commented 24 years ago

From [Unknown Contact. See original ticket]

Vicki Brown \vlb@cfcl\.com writes:

If -l returns success\, then the file (a link) must also exist; but under certain circumstances\, -e fails.

This is actually useful for finding broken links.

-- Nick Ing-Simmons \nik@tiuk\.ti\.com Via\, but not speaking for: Texas Instruments Ltd.

p5pRT commented 24 years ago

From @vlbrown

At 20:55 -0400 08/12/1999\, Mark-Jason Dominus wrote:

-e tests the existence of the *file that is linked to*\, not the existence of the link itself. Thus -e on a dangling symlink will return false.

Ahhhh. A subtlety not clear from the docs. -- -- |\ _\,\,\,---\,\,_ Vicki Brown \vlb@cfcl\.com ZZZzz /\,`.-'`' -. ;-;;\,_ Journeyman Sourceror: Scripts & Philtres |\,4- ) )-\,_. \,\ ( `'-' P.O. Box 1269 San Bruno CA 94066 '---''(_/--' `-'\_) http://www.cfcl.com/~vlb http://www.macperl.com

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