Understanding CHMOD

[Fuzzyman]

Ok.... so I might be a windoze user trying to program CGIs for a Linux
server.... but Python doesn't seem to go out of it's way to make
understanding file attributes difficult. The python manual is
appalling in this are a :-(

Anyway - I think I've finally worked out that the correct way to get
(rather than set) the mode of a file is :

from stat import *
S_IMODE(os.stat (filepath)[ST_MODE])

Obvious huh !

The result will be some bitmasked combination of the following ?

statlist = [S_ISUID, S_ISGID, S_ENFMT, S_ISVTX, S_IREAD, S_IWRITE,
S_IEXEC, S_IRWXU, S_IRUSR, S_IWUSR, S_IXUSR, S_IRWXG,
S_IRGRP, S_IWGRP, S_IXGRP, S_IRWXO, S_IROTH, S_IWOTH, S_IXOTH]

Which mean ??????

Having obtained a result from S_IMODE(os.stat (filepath)[ST_MODE]), how
do I work out what it means ?

Thanks.

Fuzzy

http://www.voidspace.org.uk/atlantibots/pythonutils.html

[Paul Rubin]

Re: Understanding CHMOD

What's your question? I think you need to look at the chmod(1) and
chmod(2) Linux man pages, not a Python manual.

[Ben Finney]

Re: Understanding CHMOD

On 13 Feb 2004 00:55:30 -0800, Fuzzyman wrote:[color=blue]
> Ok.... so I might be a windoze user trying to program CGIs for a Linux
> server.... but Python doesn't seem to go out of it's way to make
> understanding file attributes difficult. The python manual is
> appalling in this are a :-([/color]

The library reference seems to detail all the points that were confusing
you. The documentation for the 'stat' module in particular seems pretty
explicit:

<http://www.python.org/doc/current/lib/module-stat.html>

--
\ "There is no reason anyone would want a computer in their |
`\ home." -- Ken Olson, president, chairman and founder of |
_o__) Digital Equipment Corp., 1977 |
Ben Finney <http://bignose.squidly .org/>

[Tim Daneliuk]

Re: Understanding CHMOD

Fuzzyman wrote:
[color=blue]
> Ok.... so I might be a windoze user trying to program CGIs for a Linux
> server.... but Python doesn't seem to go out of it's way to make
> understanding file attributes difficult. The python manual is
> appalling in this are a :-([/color]

These are Unix-style permissions and the right place to
get more info would be a Unix OS man page for 'chmod'.

As it happens, last year, I wrote a Python program that
examines file attributes portably across Win32 and Unix.
You can have a look at the code that does this (among many
other things) at:

http://www.tundraware.com/Software/twander/

[color=blue]
>
> Anyway - I think I've finally worked out that the correct way to get
> (rather than set) the mode of a file is :
>
> from stat import *
> S_IMODE(os.stat (filepath)[ST_MODE])
>
> Obvious huh !
>
> The result will be some bitmasked combination of the following ?
>
> statlist = [S_ISUID, S_ISGID, S_ENFMT, S_ISVTX, S_IREAD, S_IWRITE,
> S_IEXEC, S_IRWXU, S_IRUSR, S_IWUSR, S_IXUSR, S_IRWXG,
> S_IRGRP, S_IWGRP, S_IXGRP, S_IRWXO, S_IROTH, S_IWOTH, S_IXOTH]
>
> Which mean ??????
>
> Having obtained a result from S_IMODE(os.stat (filepath)[ST_MODE]), how
> do I work out what it means ?
>
> Thanks.
>
> Fuzzy
>
> http://www.voidspace.org.uk/atlantib...thonutils.html[/color]


--
----------------------------------------------------------------------------
Tim Daneliuk tundra@tundrawa re.com
PGP Key: http://www.tundraware.com/PGP/

[P@draigBrady.com]

Re: Understanding CHMOD

Fuzzyman wrote:[color=blue]
> Ok.... so I might be a windoze user trying to program CGIs for a Linux
> server.... but Python doesn't seem to go out of it's way to make
> understanding file attributes difficult. The python manual is
> appalling in this are a :-([/color]

agreed
[color=blue]
> Anyway - I think I've finally worked out that the correct way to get
> (rather than set) the mode of a file is :
>
> from stat import *
> S_IMODE(os.stat (filepath)[ST_MODE])
>
> Obvious huh !
>
> The result will be some bitmasked combination of the following ?
>
> statlist = [S_ISUID, S_ISGID, S_ENFMT, S_ISVTX, S_IREAD, S_IWRITE,
> S_IEXEC, S_IRWXU, S_IRUSR, S_IWUSR, S_IXUSR, S_IRWXG,
> S_IRGRP, S_IWGRP, S_IXGRP, S_IRWXO, S_IROTH, S_IWOTH, S_IXOTH]
>
> Which mean ??????
>
> Having obtained a result from S_IMODE(os.stat (filepath)[ST_MODE]), how
> do I work out what it means ?[/color]

These are the basic access permissions.

S_IRGRP
S_IROTH
S_IRUSR

S_IWGRP
S_IWOTH
S_IWUSR

S_IXGRP
S_IXOTH
S_IXUSR

There are some shortcut (confusing IMHO) entries:

S_IEXEC = S_IXUSR
S_IWRITE = S_IWUSR
S_IREAD = S_IRUSR

S_IRWXG = stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP
S_IRWXO = stat.S_IROTH | stat.S_IWOTH | stat.S_IXOTH
S_IRWXU = stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR

The rest are "extended" attribute bits
and file type bits.

Here's a simplified ls access listing in python:

#!/usr/bin/env python

import sys
import stat
import os

filename=sys.ar gv[1]
mode=stat.S_IMO DE(os.lstat(fil ename)[stat.ST_MODE])
perms="-"
for who in "USR", "GRP", "OTH":
for what in "R", "W", "X":
if mode & getattr(stat,"S _I"+what+who) :
perms=perms+wha t.lower()
else:
perms=perms+"-"
print perms + " " + filename

--
Pádraig Brady - http://www.pixelbeat.org

[Fuzzyman]

Re: Understanding CHMOD

[snip..][color=blue]
>
> These are the basic access permissions.
>
> S_IRGRP
> S_IROTH
> S_IRUSR
>
> S_IWGRP
> S_IWOTH
> S_IWUSR
>
> S_IXGRP
> S_IXOTH
> S_IXUSR
>
> There are some shortcut (confusing IMHO) entries:
>
> S_IEXEC = S_IXUSR
> S_IWRITE = S_IWUSR
> S_IREAD = S_IRUSR
>
> S_IRWXG = stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP
> S_IRWXO = stat.S_IROTH | stat.S_IWOTH | stat.S_IXOTH
> S_IRWXU = stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR
>
> The rest are "extended" attribute bits
> and file type bits.
>
> Here's a simplified ls access listing in python:
>
> #!/usr/bin/env python
>
> import sys
> import stat
> import os
>
> filename=sys.ar gv[1]
> mode=stat.S_IMO DE(os.lstat(fil ename)[stat.ST_MODE])
> perms="-"
> for who in "USR", "GRP", "OTH":
> for what in "R", "W", "X":
> if mode & getattr(stat,"S _I"+what+who) :
> perms=perms+wha t.lower()
> else:
> perms=perms+"-"
> print perms + " " + filename[/color]

Thanks for your help !
I always find it slightly surprising when I get a reply that actually
answers the question ;-)

Fuzzy

http://www.voidspace.org.uk/atlantibots/pyhtonutils.html

[Fuzzyman]

Re: Understanding CHMOD

Tim Daneliuk <tundra@tundraw are.com> wrote in message news:<bfhuf1-b0u.ln1@eskimo. tundraware.com> ...[color=blue]
> Fuzzyman wrote:
>[color=green]
> > Ok.... so I might be a windoze user trying to program CGIs for a Linux
> > server.... but Python doesn't seem to go out of it's way to make
> > understanding file attributes difficult. The python manual is
> > appalling in this are a :-([/color]
>
> These are Unix-style permissions and the right place to
> get more info would be a Unix OS man page for 'chmod'.
>
> As it happens, last year, I wrote a Python program that
> examines file attributes portably across Win32 and Unix.
> You can have a look at the code that does this (among many
> other things) at:
>
> http://www.tundraware.com/Software/twander/[/color]

Thanks very much.
I'll have a look - much appreciated.

Fuzzy

http://www.voidspace.org.uk/atlantibots/pyhtonutils.html

[color=blue]
>
>[color=green]
> >
> > Anyway - I think I've finally worked out that the correct way to get
> > (rather than set) the mode of a file is :
> >
> > from stat import *
> > S_IMODE(os.stat (filepath)[ST_MODE])
> >
> > Obvious huh !
> >
> > The result will be some bitmasked combination of the following ?
> >
> > statlist = [S_ISUID, S_ISGID, S_ENFMT, S_ISVTX, S_IREAD, S_IWRITE,
> > S_IEXEC, S_IRWXU, S_IRUSR, S_IWUSR, S_IXUSR, S_IRWXG,
> > S_IRGRP, S_IWGRP, S_IXGRP, S_IRWXO, S_IROTH, S_IWOTH, S_IXOTH]
> >
> > Which mean ??????
> >
> > Having obtained a result from S_IMODE(os.stat (filepath)[ST_MODE]), how
> > do I work out what it means ?
> >
> > Thanks.
> >
> > Fuzzy
> >
> > http://www.voidspace.org.uk/atlantib...thonutils.html[/color][/color]