Some python questions (building cgi website)

[paul h]

hi there,
i'm learning to use python for cgi, and i've hit a few road blocks.
basically, i need to know how to achieve the following things using
python, on linux.
create a new directory, and sub-directory.
so if the user inputs "HELLO", i can create a dir called HELLO, and
then some other dirs in there.

i also need to know how i can write various things into a file.
the following doesnt seem to work for me:
file.write("TEX T HERE")
how can i write plain text into a file?


any help with these questions would be great!
cheers,
paul

[Alex Martelli]

Re: Some python questions (building cgi website)

paul h wrote:
[color=blue]
> hi there,
> i'm learning to use python for cgi, and i've hit a few road blocks.
> basically, i need to know how to achieve the following things using
> python, on linux.
> create a new directory, and sub-directory.
> so if the user inputs "HELLO", i can create a dir called HELLO, and
> then some other dirs in there.[/color]

Assuming that:
1. your process's current directory is the one you want to
have as the parent of 'HELLO';
2. your process is running as a user that has permission to
write in its current directory;
3. there is no subdirectory named 'HELLO' in the current
directory;
4. some variable, say X, refers to the string which in this
case happens to be 'HELLO';

then:

import os
os.mkdir(X)

will make that 'HELLO' subdirectory, and then, e.g.:

os.mkdir(X + '/foop')

will create a subdirectory foop of that HELLO subdirectory.

All these points, especially 1-2, cannot be taken for granted
since your process is running as a CGI script; you must ensure
by administrative means that your process is running as the user
you desire (Python or any other language is powerless to help
you there!) and either administrativel y or programmaticall y
ensure the current directory is the one you want (or that you
know the full path to prepend to X) -- the latter may not be
trivial if chroot is in play, as it should be in most well-run
network servers, for security reasons.

[color=blue]
> i also need to know how i can write various things into a file.
> the following doesnt seem to work for me:
> file.write("TEX T HERE")
> how can i write plain text into a file?[/color]

You need to OPEN a file for writing first:

x = file('thefile.t xt', 'w')

and THEN you can call x.write("TEST HERE") to write some string
(in this case, one without a terminating newline). file.write
is an unbound method of built-in type file and, called as you
mean to, would have no possible idea on WHAT file to write on!!!


Alex

[Matt Goodall]

Re: Some python questions (building cgi website)

paul h wrote:
[color=blue]
>hi there,
>i'm learning to use python for cgi, and i've hit a few road blocks.
>basically, i need to know how to achieve the following things using
>python, on linux.
>create a new directory, and sub-directory.
>so if the user inputs "HELLO", i can create a dir called HELLO, and
>then some other dirs in there.
>
>[/color]
See os.mkdir() or os.makedirs().

Please be *very* careful letting users access the file system in this
way. Consider the situation where the user enters "/HELLO",
"../../HELLO" etc - they could do all sorts of damage! You should
probably restrict directory creation to a certain area of the file
system. os.path.normpat h() can be useful in working out what the user's
input really means.
[color=blue]
>i also need to know how i can write various things into a file.
>the following doesnt seem to work for me:
>file.write("TE XT HERE")
>how can i write plain text into a file?
>
>[/color]
Unless you have created an object reference called file then file is
actually a builtin for *opening* a file, or rather for creating a file
object.

This is probably what you want:

file('thefile.t xt','wt').write ('TEXT HERE')

or better still

f = file('thefile.t xt','wt')
try:
f.write('TEXT HERE')
finally:
if f:
f.close()

which will ensure the file is closed correctly.

Cheers, Matt

--
Matt Goodall, Pollenation Internet Ltd
w: http://www.pollenation.net
e: matt@pollenatio n.net