Stupid question: Making scripts python-scripts

[Jan Danielsson]

Hello all,

How do I make a python script actually a _python_ in unix:ish
environments?

I know about adding:
#!/bin/sh

..as the first row in a shell script, but when I installed python on
a NetBSD system, I didn't get a "python" executable; only a "python2.4"
executable.

Adding "#!/usr/pkg/bin/python2.4" as the first row in the script
would probably work, but that would be too specific for the system I'm
using, imho.

I saw someone using "#!/usr/bin/env python", but that failed on the
system I'm using, so I assume that's something specific too (or is the
installation broken?).

[callmebill]

On your system, do:
which python2.4

That will give you the full path to the python2.4 binary (let's call it
"path/to/py24").

Then add:
#!/path/to/py24

....to the top of your script.

And make sure the file is chmod'd +x

[callmebill]

oops... I missed the "too specific comment." Sorry =)

[callmebill]

You could also set your "python" environment variable on the system...
set it to be "/path/to/python2.4". Then use the "#!/usr/bin/env
python" trick. Just make sure that env is working for you, first.

[Bill Mill]

On 7/21/05, Bill Mill <bi*******@gmail.com> wrote:

On 7/21/05, Jan Danielsson <ja************@gmail.com> wrote:

Hello all,

How do I make a python script actually a _python_ in unix:ish
environments?

I know about adding:
#!/bin/sh

..as the first row in a shell script, but when I installed python on
a NetBSD system, I didn't get a "python" executable; only a "python2.4"
executable.

Adding "#!/usr/pkg/bin/python2.4" as the first row in the script
would probably work, but that would be too specific for the system I'm
using, imho.

I saw someone using "#!/usr/bin/env python", but that failed on the
system I'm using, so I assume that's something specific too (or is the
installation broken?).

The env program [1], which usually exists at least on a linux system,
executes the program given as its argument. Thus, "/usr/bin/env
python" tries to executes python, which bash will then use to run the
python script. As long as env exists, and python is somewhere in the
PATH, this is a fairly portable way to run python scripts.

Does BSD really not come with the env program? I bet there's an
equivalent you could symlink to it. Unfortunately, I've never BSDed,
so I can't help you find it. To get a workable subset of the normal
env functionality, you could try (assuming you use bash):

/home/llimllib $ echo "$@" > /usr/bin/env
/home/llimllib $ chmod a+x /usr/bin/env

ahhh, that should be:

/home/llimllib $ echo "\$@" > /usr/bin/env

otherwise bash tries to substitute into the string. Sorry bout that.

Peace
Bill Mill
bill.mill at gmail.com

[Bill Mill]

On 7/21/05, Jan Danielsson <ja************@gmail.com> wrote:

Hello all,

How do I make a python script actually a _python_ in unix:ish
environments?

I know about adding:
#!/bin/sh

..as the first row in a shell script, but when I installed python on
a NetBSD system, I didn't get a "python" executable; only a "python2.4"
executable.

Adding "#!/usr/pkg/bin/python2.4" as the first row in the script
would probably work, but that would be too specific for the system I'm
using, imho.

I saw someone using "#!/usr/bin/env python", but that failed on the
system I'm using, so I assume that's something specific too (or is the
installation broken?).

The env program [1], which usually exists at least on a linux system,
executes the program given as its argument. Thus, "/usr/bin/env
python" tries to executes python, which bash will then use to run the
python script. As long as env exists, and python is somewhere in the
PATH, this is a fairly portable way to run python scripts.

Does BSD really not come with the env program? I bet there's an
equivalent you could symlink to it. Unfortunately, I've never BSDed,
so I can't help you find it. To get a workable subset of the normal
env functionality, you could try (assuming you use bash):

/home/llimllib $ echo "$@" > /usr/bin/env
/home/llimllib $ chmod a+x /usr/bin/env

Peace
Bill Mill
bill.mill at gmail.com

[1]: http://rootr.net/man/man/env/1

[bruno modulix]

Jan Danielsson wrote:

Hello all,

How do I make a python script actually a _python_ in unix:ish
environments?

I know about adding:
#!/bin/sh

..as the first row in a shell script, but when I installed python on
a NetBSD system, I didn't get a "python" executable; only a "python2.4"
executable.

Adding "#!/usr/pkg/bin/python2.4" as the first row in the script
would probably work, but that would be too specific for the system I'm
using, imho.
What about:

ln /usr/pkg/bin/python2.4 /usr/bin/python

then
#!/usr/bin/python

in your script, and you should be done (dont forget to chmod +x your
script of course)

Or I'm I missing something specific to xxxBSD ?
I saw someone using "#!/usr/bin/env python", but that failed on the
system I'm using,

How do you execute the python interpreter ? If you need to type
"python2.4" (not just "python"), then obviously 'usr/bin/env python'
syntax shouldn't work either.

My 2 cents
--
bruno desthuilliers
python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in 'o****@xiludom.gro'.split('@')])"

[Benjamin Niemann]

Jan Danielsson wrote:

Hello all,

How do I make a python script actually a _python_ in unix:ish
environments?

I know about adding:
#!/bin/sh

..as the first row in a shell script, but when I installed python on
a NetBSD system, I didn't get a "python" executable; only a "python2.4"
executable.

Adding "#!/usr/pkg/bin/python2.4" as the first row in the script
would probably work, but that would be too specific for the system I'm
using, imho.

I saw someone using "#!/usr/bin/env python", but that failed on the
system I'm using, so I assume that's something specific too (or is the
installation broken?).

You could
a) create a symlink to your python executable in a well known location, e.g.
ln -s /usr/pkg/bin/python2.4 /usr/bin/python
And use either "#!/usr/bin/python" (which should work on most UNIXoid
systems with python installed) or "#!/usr/bin/env python"

b) use the absolute path /usr/pkg/bin/python2.4 for your script (in order to
have it running on your system) and use distutils to create a setup.py
script for distribution. IIRC setup.py will recognize the shebang of your
scripts and replace it with the proper path to python of the target system
during installation.

--
Benjamin Niemann
Email: pink at odahoda dot de
WWW: http://www.odahoda.de/

[Mike Meyer]

Bill Mill <bi*******@gmail.com> writes:

On 7/21/05, Jan Danielsson <ja************@gmail.com> wrote:

Hello all,

How do I make a python script actually a _python_ in unix:ish
environments?

I know about adding:
#!/bin/sh

..as the first row in a shell script, but when I installed python on
a NetBSD system, I didn't get a "python" executable; only a "python2.4"
executable.

Adding "#!/usr/pkg/bin/python2.4" as the first row in the script
would probably work, but that would be too specific for the system I'm
using, imho.

I saw someone using "#!/usr/bin/env python", but that failed on the
system I'm using, so I assume that's something specific too (or is the
installation broken?).
The env program [1], which usually exists at least on a linux system,
executes the program given as its argument. Thus, "/usr/bin/env
python" tries to executes python, which bash will then use to run the
python script. As long as env exists, and python is somewhere in the
PATH, this is a fairly portable way to run python scripts.

env doesn't invoke the shell, it uses execvp, which "duplicates the
actions of the shell in searching for an executable." Further, he's on
NetBSD - he may not have bash installed. My FreeBSD box certainly
doesn't.
Does BSD really not come with the env program? I bet there's an
equivalent you could symlink to it. Unfortunately, I've never BSDed,
so I can't help you find it. To get a workable subset of the normal
env functionality, you could try (assuming you use bash):

NetBSD comes with an env. His env is failing because he doesn't have a
"python" command installed.

This appears to be wart(?) in the NetBSD packaging system. To allow
multiple versions of FreeBSD to coexist, it doesn't install a "python"
command at all, but instead leaves the versioned one around.

Two solutions: have your scripts use #!/usr/pkg/bin/python2.4. That
way, when you install a new python, they will keep using the old
one. That will insure they won't break when you upgrade.

However, such breakage is pretty rare in practice. I'd pick a favorite
bin directory and symlink from python there to /usr/pkg/bin/python2.4,
then use "#!/usr/bin/env python" in your scripts.

While I'm on the topic, I think I'll share my favorite cool trick.

#!/usr/opt/bin/mypythonscript

Doesn't work because Unix won't let you use an interpreted script as
the interpreter (is this true for all variants?). However,

#!/usr/bin/env mypythonscript

works like a charm.

<mike
--
Mike Meyer <mw*@mired.org> http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.