bash scripting: how to find the absolute path of "symlink/.."?

Question

Given two files:

generic/scripts/hello.sh
parent/scripts -> generic/scripts

Upon calling parent/scripts/hello.sh from any location, I would like (in the script) to find the full path of the parent directory. In this case parent.

The main issue is that parent/scripts/.. refers to generic in unix. On the other hand, everything involving regexes is not generic and may be error prone.

Solutions that don't work:

`dirname $0`/..
realpath  `dirname $0`/..
readlink -f `dirname $0`/..
`cd *something*/..; pwd`
`perl ... abs_path(...)`

All these will point to generic and not parent because of the symbolic link.

Everything involving regular expressions are not adaptable/generic, may fail for more complexes paths. There might be other .. and symlinks in the path, you want the grand-parent, it's a directory name involving .., you call it via $PATH...

Moreover, I would like it to work in any case, even when it is called via $PATH.

Any simple safe solution for this simple problem? I mean it's just getting the parent directory after all!

What I used:

dir=$( dirname $( cd `dirname $0` >/dev/null; pwd ) )

Dunno if it is perfect but it seems to behave as expected.

Roomette

how are you calling these scripts? – Ontologism

ideally, no restrictions should be put on how they can be called. – Roomette

Your first solution works as long as you are actually using the parent/scripts/hello.sh to call the script. – Ias

"...it's just getting the parent directory after all" generic is hello's parent directory, that's why all the tools you use give you that. If parent/scripts is not visible in $0, you'll not get it. On linux, cd to parent/scripts and do ls -l /proc/$$ to see what the OS knows about where you are. – Ontologism

...well ...somehow you have the information. It's either in $0 (when calling it from "outside" or $PATH), or to be combined with pwd if you are calling it within one of the subdirectories using a relative path. I just have the feeling that you have to manually handle several different cases and that you have to resolve the path using regular expressions ...which I personally think is fairly ugly ...just to get the parent. – Roomette

Answer 1

Try this:

basename $(dirname $(dirname $0))

or perhaps just

$(dirname $(dirname $0))

It is unclear if you want parent alone or its full path.

Bravura

double dirname does the trick ...the only to add is concatenating it with pwd when $0 is a relative path to also take into account the case when we are in one of the sub directories. – Roomette

double dirname does not do the trick: dirname $(dirname ../../../) results in '..'. – Shrug

@Shrug $0 is quite unlikely to be equal to ../../../ – Bravura

Answer 2

I would recommend 1) use pwd -P which will always give you the physical path, and then navigate with relative path to the other palce This is most safe.

2) use pwd -L

Logbook

Answer 3

pushd $(dirname $0)
FOO=$(pwd)
popd

That gives you the absolute path of the directory that the script is running in.

Glynisglynn

Answer 4

I call my scipt with this: ../script1 and it has a relative call to ../relative/script2

`(cd $0/.. && pwd)`/relative/script2

is in script1

Feel

Answer 5

in bash you could do some string manipulation on $PWD if that variable is available.

For pathname of parent directory, use:

${PWD%/*}

Other examples :

me@host:/tmp/bash_string/ma ni-pu_la/tion$ echo -e \
"\$PWD or \${PWD} : " $PWD \
"\n\${PWD##/*}     : " ${PWD##/*} \
"\n\${PWD##*/}     : " ${PWD##*/} \
"\n\${PWD#/*}      : " ${PWD#/*} \
"\n\${PWD#*/}      : " ${PWD#*/} \
"\n\${PWD%%/*}     : " ${PWD%%/*} \
"\n\${PWD%%*/}     : " ${PWD%%*/} \
"\n\${PWD%/*}      : " ${PWD%/*} \
"\n\${PWD%*/}      : " ${PWD%*/} \
"\n" # Gives :
$PWD or ${PWD} :  /tmp/bash_string/ma ni-pu_la/tion 
${PWD##/*}     :  
${PWD##*/}     :  tion 
${PWD#/*}      :  tmp/bash_string/ma ni-pu_la/tion 
${PWD#*/}      :  tmp/bash_string/ma ni-pu_la/tion 
${PWD%%/*}     :  
${PWD%%*/}     :  /tmp/bash_string/ma ni-pu_la/tion 
${PWD%/*}      :  /tmp/bash_string/ma ni-pu_la 
${PWD%*/}      :  /tmp/bash_string/ma ni-pu_la/tion

Maleficence

Answer 6

What about this:

echo `cd .. && pwd`

Sunstroke