Solved Resolve the full path name of an 'sh' script

[freethread]

I run in trouble resolving the full path of an sh (not bash) script or better, I want an "universal" sh function that resolve a path. I always used the following code to resolve a script path and always worked:

sScriptDir="$( realpath $( dirname $0 ) )

it works. Now I symlinked the script (relative symlink) in another directory. The directory of the symlink is /linkdir, the script is in the directory linkdir/scripts (names are fictional)

cd /linkdir
ln -s ./scripts/myscript.sh myscript

now the code line above no more works, I have to do

s1="$( realpath $( dirname $0 ) )"
s2="${s1}/$( readlink $0 )"
s3="$( realpath $s2 )"
# show result
echo "\$s1 '${s1}'"
echo "\$s2 '${s2}'"
echo "real:     '${s3}'"

I'm looking for a solution for absolute and relative symlinks

EDIT
An "universal" function for symlinks (relative and absolute) and real path (not symlinked)

 

[T-Aoki]

If the link can be hardlink instead of symlink, can't your issue resolved?
(Need to be in the same filesystem, though.)

Quick test with the simple script below as /tmp/test.sh and set executable:

#!/bin/sh

echo $0
realpath $0
readlink -f $0

In case the link is symlink /tmp/test/test.sh

% ./test.sh    # at /tmp
./test.sh
/tmp/test.sh
/tmp/test.sh
% ./test.sh    # at /tmp/test
./test.sh
/tmp/test.sh
/tmp/test.sh
%

In case the link is hardlink /tmp/test/test.sh

% ./test.sh     # at /tmp
./test.sh
/tmp/test.sh
/tmp/test.sh
% ./test.sh     # at /tmp/test
./test.sh
/tmp/test/test.sh
/tmp/test/test.sh
%

 

[SirDice]

basedir=$( dirname $(realpath $(readlink -f $0)))

dice@maelcum:~/test % ll
total 1
drwxr-xr-x  2 dice dice  3 Aug 20 14:43 scripts/
lrwxr-xr-x  1 dice dice 17 Aug 20 14:38 test@ -> ./scripts/test.sh
dice@maelcum:~/test % cat scripts/test.sh
#!/bin/sh

basedir=$( dirname $(realpath $(readlink -f $0)))

echo "$basedir"

echo "Hello World!"
dice@maelcum:~/test % ./test
/usr/home/dice/test/scripts
Hello World!
dice@maelcum:~/test % scripts/test.sh
/usr/home/dice/test/scripts
Hello World!

Doesn't work for hard-links though

dice@maelcum:~/test % ln ./scripts/test.sh hard_test
dice@maelcum:~/test % ./hard_test
/usr/home/dice/test
Hello World!

 

[freethread]

Great. I only need symlinks and no links. Many thanks to T-Aoki and SirDice for the solution. I spent all the morning to try to get a solution, the search point me to readlink, but info stated that only GNU tools and not in BSD, but a quick whereis readlink show it is in base system. Thank you all