[Subodh21]

Hi i am new to learning BASH and wondering if someone here can explain me what this bash code is doing.

#!/bin/sh

usage () {
exec 1>&2
while [ "$#" -ge 1 ]; do echo "$1"; shift; done
cat <<USAGE
Usage: ${0##*/} [OPTIONS]

Options:
-i | -interface no refinment in vertical direction of the mesh
-l | -local mesh with local refinment
-h | -help help

Ship hull simulation to demonstrate two different meshing strategies that can be
used with PLIC type schemes.

USAGE
exit 1
}

meshType=0

# OPTIONS
while [ "$#" -gt 0 ]
do
case "$1" in
-i | -interface)
meshType=1
break
;;
-l | -local)
meshType=2
break
;;
-h | -help)
usage
;;
-test)
shift
;;
-*)
usage "Invalid option '$1'"
;;
*)
usage "Invalid option '$1'"
break
;;
esac
done


# Run from this directory
cd "${0%/*}" || exit 1

# Source tutorial run functions
. "$WM_PROJECT_DIR/bin/tools/RunFunctions"

if [ $meshType -eq 0 ] || [ $meshType -eq 1 ]; then
{
./Allmesh.1
}
elif [$meshType -eq 2 ]; then
{
./Allmesh.2
}
fi

runApplication setFields

runApplication decomposePar

runParallel $(getApplication)

runApplication reconstructPar

#------------------------------------------------------------------------------


Thanks in advance!!

[Tobermory]

Okay, well here goes:

#!/bin/sh

defines this script as a Bourne shell script; note that if you want it to be interpreted as a bash script, then this should be /bin/bash

usage ()
   ...
}

defines a function that prints out help info on how to run the command

while [ "$#" -gt 0 ]
do
  case "$1" in
    -i | -interface)
      meshType=1
      break
      ;;
    -l | -local)
      meshType=2
      break
      ;;
    -h | -help)
      usage
      ;;
    -test)
      shift
      ;;
    -*)
      usage "Invalid option '$1'"
      ;;
    *)
      usage "Invalid option '$1'"
      break
      ;;
  esac
done

parses the parameters that the command was called with and sets variable meshType

cd "${0%/*}" || exit 1

changes working directory to the folder that this file is located in (without this command, if you called the script from another folder then the working directory would be that other folder)

. "$WM_PROJECT_DIR/bin/tools/RunFunctions"

loads the macro functions from this OF script (includes runApplication etc.)

if [ $meshType -eq 0 ] || [ $meshType -eq 1 ]; then
  {
    ./Allmesh.1
  }
elif [$meshType -eq 2 ]; then
  {
   ./Allmesh.2
  }
fi

run Allmesh.1 if meshType is 0 or 1, or Allmesh.2 if it's 2.

runApplication setFields
runApplication decomposePar

run applications setFields and decomposePar (single core)

runParallel $(getApplication)
runApplication reconstructPar

get the application name from the controlDict file and then run the application in parallel and reconstruct the processor files.

Happy?

[Subodh21]

Originally Posted by Tobermory

Okay, well here goes:

#!/bin/sh

defines this script as a Bourne shell script; note that if you want it to be interpreted as a bash script, then this should be /bin/bash

usage ()
   ...
}

defines a function that prints out help info on how to run the command

while [ "$#" -gt 0 ]
do
  case "$1" in
    -i | -interface)
      meshType=1
      break
      ;;
    -l | -local)
      meshType=2
      break
      ;;
    -h | -help)
      usage
      ;;
    -test)
      shift
      ;;
    -*)
      usage "Invalid option '$1'"
      ;;
    *)
      usage "Invalid option '$1'"
      break
      ;;
  esac
done

parses the parameters that the command was called with and sets variable meshType

cd "${0%/*}" || exit 1

changes working directory to the folder that this file is located in (without this command, if you called the script from another folder then the working directory would be that other folder)

. "$WM_PROJECT_DIR/bin/tools/RunFunctions"

loads the macro functions from this OF script (includes runApplication etc.)

if [ $meshType -eq 0 ] || [ $meshType -eq 1 ]; then
  {
    ./Allmesh.1
  }
elif [$meshType -eq 2 ]; then
  {
   ./Allmesh.2
  }
fi

run Allmesh.1 if meshType is 0 or 1, or Allmesh.2 if it's 2.

runApplication setFields
runApplication decomposePar

run applications setFields and decomposePar (single core)

runParallel $(getApplication)
runApplication reconstructPar

get the application name from the controlDict file and then run the application in parallel and reconstruct the processor files.

Happy?

Thanks Tobermory,

Appreciate your reply.
Can you expand a bit more on what these lines of code are doing

usage () {
exec 1>&2
while [ "$#" -ge 1 ]; do echo "$1"; shift; done
cat <<USAGE
Usage: ${0##*/} [OPTIONS]

Also, if you can suggest some resources to learn about Bourne shell scripts, especially from the point of view of Open foam application.
Thanks again!

[Tobermory]

Ok - let me paste the whole of the function in and run through it.

Start at the top - the following line denotes that this is a function definition

usage () {

This next line redirects stdout (ie. output from prints to screen) into stderr (the ouput for error messages)

exec 1>&2

$# holds the number of parameters that the script was called with, so the while loop keeps executing whilst there are 1 or more parameters in the stack; the code that is executed is as follows: print to the screen the first parameter ($1), then "shift", ie throw away the first parameter and shuffle all the remaining parameters up one place. So all it does it print out all the parameters.

while [ "$#" -ge 1 ]; do echo "$1"; shift; done

The following treats all of the text between the two instances of USAGE as a block of text, and cat's (ie prints) it out to screen.

cat <<USAGE
  Usage: ${0##*/} [OPTIONS]

  Options:
  -i | -interface no refinment in vertical direction of the mesh
  -l | -local mesh with local refinment
  -h | -help help

  Ship hull simulation to demonstrate two different meshing strategies that can be
  used with PLIC type schemes.

USAGE

exit is a shell command to stop the script; the 1 is an optional error code. The curly brace denotes the end of the function definition.

exit 1
}

As for good references - I can't help you there, I am afraid. The best way of learning is by doing ... and by googling: there is a LOT of useful stuff on the web, explaining bash scripts, and lots of blogs, training material etc. Good luck!

[olesen]

Originally Posted by Tobermory

As for good references - I can't help you there, I am afraid. The best way of learning is by doing ... and by googling: there is a LOT of useful stuff on the web, explaining bash scripts, and lots of blogs, training material etc. Good luck!

Nice of you to have taken the time to explain things. I agree with you that learning by doing is the best (the only?) way. There are a reason enough number of shell scripts within OpenFOAM. Combine those with "man bash" and most of it should be understandable.
For good measure, the old references are still really good:

https://tldp.org/LDP/Bash-Beginners-...tml/index.html
https://tldp.org/LDP/abs/html/

[petros]

Thanks both for the very useful information provided.