readlink -f Invalid argument

[DSL-Usr]

if [ `readlink $0` ]; then
scriptname=`readlink -f $0`
else
scriptname="$0"
fi

is the beginning of a script, not written by me. When run it returns the message;

readlink: scriptname: Invalid argument - I imagine this relates to the -f argument (option)?

Any ideas on what the author might be trying to do with -f ?

Do you think I'm correct in thinking -f is the problem?

The readlink does stick ./ on the front of the scriptname and I'm also guessing this is both normal and correct? Is that normal and correct?

Any help? Any ideas? Please Please Please

[drl]

Hi.

The fragment seems to work for me in this:

#!/usr/bin/env bash

# @(#) s1       Demonstrate readlink.

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) readlink
set -o nounset

echo
echo " Results:"
if [ `readlink $0` ]
then
  scriptname=`readlink -f $0`
else
  scriptname="$0"
fi

echo " scriptname is :$scriptname:"

exit 0

Running as s1:

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.11-x1, i686
Distribution        : Xandros Desktop 3.0.3 Business
GNU bash 2.05b.0
readlink (coreutils) 5.2.1

 Results:
 scriptname is :./s1:

and running as a soft link my_link1:

% ./my_link1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.11-x1, i686
Distribution        : Xandros Desktop 3.0.3 Business
GNU bash 2.05b.0
readlink (coreutils) 5.2.1

 Results:
 scriptname is :/home/drl/try/user-problem/575/s1:

It might be useful to place the fragment in a short test script as I did, and then paste the code and the result.

Just a guess -- are you using a really old Linux system? ... cheers, drl

[DSL-Usr]

Hi drl, thanks for your reply

Here's what I put in;

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) readlink
set -o nounset

echo
echo " Results:"
if [ `readlink $0` ]
then
scriptname=`readlink -f $0`
else
scriptname="$0"
fi

echo " scriptname is :$scriptname:"

exit 0

And here-s what I got out

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")

Results:
readlink: ./freecast-tracker: Invalid argument
scriptname is : ./freecast-tracker

I used the same filename as previously, to continue as consistent as possible.

I'm using DSL (damn small linux) which uses a 1.4 kernel and it's on an old P1 laptop. It's the only distro for old style machines I could get to boot and run and install as a layman (I'm not a linux bod, give me point and click every time lol).

Version didn't seem to work here? (I can do java -version and it gives me a return).

I probably haven't loaded dsl up with all the possible goodies, can't remember if I did GNU Utils etc this time round as, when the electricity clicks off, as it does here in Spain reasonably often, the fs goes wonky and I've had to reinstall, and I try only to download the minimum I think I may need to do the job I want to do.

Does any of this mean anything to you? Do you know what that -f might be supposed to do?

Thanks for any more help you can give?

[drl]

Hi.

The version control statement is local to my site. It is set up in the script so that it is a do-nothing if it is not available.

Does your man page look like this?

SYNOPSIS
       readlink [OPTION]... FILE

DESCRIPTION
       Display value of a symbolic link on standard output.

       -f, --canonicalize
              canonicalize  by  following  every symlink in every component of
              the given path recursively

-- excerpt from man readlink

cheers, drl

[DSL-Usr]

Hi again, very quick, thanks

Ok, man page says

readlink [-f] FILE

Display the value of a symlink

Options:

-f Canonicalize by following all symlinks

Well, I'm more in the habit of searching on the net than in man pages. Canonicalise doesn't appear in my dictionary, does it mean to follow the links in a saintly or religious fashion?

Doesn't readlink $0 just mean that it´s trying to return the name of the current script? In which case would it ever be able to return any more than this unique value however many symlinks were searched? In which case wouldn't -f be completely redundant. So, is the error being produced because the command is unable to associate the -f option with the $0?

Would the -f option become relevant when the command was being given a directory path to search, in which case it may be able to continue returning values depending however many it might find? Of course, then it would really be readlink [option] dir rather than file.

Yes, it's true, I haven't really got any idea what symlinks are or do, but am I close-ish?

[DSL-Usr]

Damn, I just took the -f out of the test script and still got the same error

Damn!

Any more help? (asking in saintly and religious piety)

[drl]

Hi.

Links are alternate names for files. They can be hard links or soft links. The readlink command allows one to follow the softlink until it gets to the real file.

Now that we know your version of readlink allows option "-f", we can move ahead to other possibilities. Please add the following line:

echo " name of script is :$0:"

before the first echo statement.

I also noticed that the first line of the script --

#!/usr/bin/env bash

was not in the report of your test script -- is that truly in the file? ... cheers, drl

[DSL-Usr]

Hmm, I don't have a directory /usr/bin/env - there's no env

Lines preceded by # are comments only and not processed by scripts? Am I missing something subtle here?

Anyway, I`ll do it just as you say, as you're technical

I did stick in a few echo's to see where the little script was going, it seems not to like if [ 'readlink $0`] and has been moving straight on to else. after I put some exho's in it seemed to process then and produced the full directory path of the script and not just the script name (preceded by ./)

Ok, brb

[DSL-Usr]

Ok, output now reads;

(versions displayed .......
name of script is :./freecast-tracker:

Results:
readlink: ./freecast-tracker: Invalid argument
scriptname is :./freecast-tracker:

[drl]

Hi.

The first line of a script often is:

#!somepath-to-an-executable

if you don't have /usr/bin/env, then please make this the first line:

#!/bin/bash

That first line would be taken as a comment, but the "#!" makes it special. You may see it referred to as a shebang line: she for shell, and bang is an old unix name for the exclamation point ... cheers, drl