Question

I need some help understanding following shell script line,

apphome =     "`cd \`dirname $0\` && pwd && cd - >/dev/null`"

All I understand is, this is creating a variable called apphome.

Answer 1

This is not a valid shell code.

The shell don’t allow spaces around =

For the rest, while this seems broken, it try to cd to the dir of the script itself, display the current dir & finally cd back to the latest cd place redirecting his standard output STDOUT to the /dev/null trash-bin (that’s makes not any sense, cd display only on standard error STDERR when it fails, never on STDOUT)

If you want to do this in a proper a simple way :

apphome="$(dirname $0)"

That’s all you need.

NOTE

The backquote

`

is used in the old-style command substitution, e.g.

foo=`command`

The

foo=$(command)

syntax is recommended instead. Backslash handling inside $() is less surprising, and $() is easier to nest. See http://mywiki.wooledge.org/BashFAQ/082