http://en.wikipedia.org/wiki/Bash_%28Unix_shell%29
http://en.wikipedia.org/wiki/Bash_%28Unix_shell%29
For instance, let s say I want to use a Bash script as a launcher for another application. I want to change the working directory to the one where the Bash script is located, so I can operate on the files in that directory, like so:
$ ./application
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
is a useful one-liner which will give you the full directory name of the script no matter where it is being called from.
It will work as long as the last component of the path used to find the script is not a symlink (directory links are OK). If you also want to resolve any links to the script itself, you need a multi-line solution:
SOURCE="${BASH_SOURCE[0]}"
while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symlink
DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
SOURCE="$(readlink "$SOURCE")"
[[ $SOURCE != /* ]] && SOURCE="$DIR/$SOURCE" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located
done
DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
This last one will work with any combination of aliases, source, bash -c, symlinks, etc.
http://bosker.wordpress.com/2012/02/12/bash-scripters-beware-of-the-cdpath/
http://bosker.wordpress.com/2012/02/12/bash-scripters-beware-of-the-cdpath/
To understand how it works, try running this more verbose form:
#!/bin/bash
SOURCE="${BASH_SOURCE[0]}"
while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symlink
TARGET="$(readlink "$SOURCE")"
if [[ $TARGET == /* ]]; then
echo "SOURCE $SOURCE is an absolute symlink to $TARGET "
SOURCE="$TARGET"
else
DIR="$( dirname "$SOURCE" )"
echo "SOURCE $SOURCE is a relative symlink to $TARGET (relative to $DIR )"
SOURCE="$DIR/$TARGET" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located
fi
done
echo "SOURCE is $SOURCE "
RDIR="$( dirname "$SOURCE" )"
DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"
if [ "$DIR" != "$RDIR" ]; then
echo "DIR $RDIR resolves to $DIR "
fi
echo "DIR is $DIR "
And it will print something like:
SOURCE ./scriptdir.sh is a relative symlink to sym2/scriptdir.sh (relative to . )
SOURCE is ./sym2/scriptdir.sh
DIR ./sym2 resolves to /home/ubuntu/dotfiles/fo fo/real/real1/real2
DIR is /home/ubuntu/dotfiles/fo fo/real/real1/real2
http://stackoverflow.com/questions/59895/getting-the-source-directory-of-a-bash-script-from-within