translate a short csh script to bash

Shell Programming and Scripting
1

Hi,

I have a csh:

  set NODES = `cat $HOST_FILE`
  set NODELIST = $TMPDIR/namd2.nodelist
  echo group main >! $NODELIST
  foreach node ( $NODES )
    echo host $node >> $NODELIST
  end
  @ NUMPROCS = 2 * $#NODES

I am very frustrated to translate it to bash:

NODES = `cat $HOST_FILE`
NODELIST = $TMPDIR/namd2.nodelist
echo group main > NODELIST1
for  node in $NODES
do
    echo host $node >> $NODELIST
done
NUMPROCS = 2 * $#NODES

The script basically capture each line of file $NODELIST and add 'host' to the beginning of each line.
Can some please help to fix my translation?
Your time is greatly appreciated!
Todd

2

PLease, put code tags for your next post.

# NODES = `cat $HOST_FILE`
NODES=$(cat $HOST_FILE) # no spaces around '=' for a value affectation
# NODELIST = $TMPDIR/namd2.nodelist
NODELIST=$TMPDIR/namd2.nodelist # same as above
echo group main > NODELIST1
for node in $NODES
do
   echo host $node >> $NODELIST
done
# NUMPROCS = 2 * $#NODES
NUMPROCS=$((2 * ${#NODES})) # $(( )) is the construction for arithmetic evaluation
3

If you're nodes are separated by lines, a safer method would be:

HOST_FILE=<your path to host file>

NODES=()

while read; do
	NODES[${#NODES[@]}]=$REPLY
done < "$HOST_FILE"

NODESLIST=$TMPDIR/namd2.nodelist

echo "group main" > "$NODESLIST"

for NODE in "${NODES[@]}"; done
	echo "host $NODE" >> "$NODESLIST"
done

(( NUMPROCS = 2 * ${#NODES[@]} ))

And a simpler version could also be like this:

HOST_FILE=<your path to host file>
NODESLIST=$TMPDIR/namd2.nodelist
NODESCOUNT=0

{
	echo "group main"

	while read; do
		echo "nodes $REPLY"

		(( NODESCOUNT++ ))
	done < "$HOST_FILE"
} > "$NODESLIST"

(( NUMPROCS = 2 * NODESCOUNT ))

It can also be further simplified if you can use readarray or mapfile from bash 4.0+.

4

frans and konsolebox,
They worked.

Thanks a lot! Appreciate your help.