[random_ran]

I notice that OpenFOAM use this command almost in every tutorial:

#+BEGIN_SRC sh
cd ${0%/*} || exit 1 # Run from this directory
#+END_SRC

I usually delete this line then execute: `./Allrun'

I checkout the bash manual ( This is Edition 4.2, last updated 28
December 2010, of 'The GNU Bash Reference Manual', for 'Bash', Version
4.2. )

At the page: 3.4.2 Special Parameters

#+BEGIN_QUOTE
'0'
Expands to the name of the shell or shell script. This is set at
shell initialization. If Bash is invoked with a file of commands
(*note Shell Scripts:, '$0' is set to the name of that file. If
Bash is started with the '-c' option (*note Invoking Bash:, then
'$0' is set to the first argument after the string to be executed,
if one is present. Otherwise, it is set to the filename used to
invoke Bash, as given by argument zero.

#+END_QUOTE

I also check '-c' option on page: 6.1 Invoking Bash
#+BEGIN_QUOTE
'-c STRING'
Read and execute commands from STRING after processing the options,
then exit. Any remaining arguments are assigned to the positional
parameters, starting with '$0'.

#+END_QUOTE

Interesting, when I use the command: `bash -c ./Allrun

It works.


Why they put this line here?

[zwlwf]

Just as the comment tells : # Run from this directory.

${i%pattern} is a bash operator, which means remove the least pattern from the end of variable i . For an example, $0 is /home/xxx/a.out, '/*' matches the /a.out, so ${0%/*} becomes /home/xxx, that is the directory of execuatable file, a.out.