&FCI
NORB=280,
NELEC=78,
MS2=0,
UHF=.FALSE.,
ORBSYM=1,1,1,1,1,1,1,1,<...>
&END
  1.48971678130072078261E+01   1   1   1   1
 -1.91501428271686324756E+00   1   1   2   1
  4.38796949990802698238E+00   1   1   2   2

&FCI NORB=280, NELEC=78, MS2=0, UHF=.FALSE.,
ORBSYM=1,1,1,1,1,1,1,1,<...>
ISYM=1,
/
  1.48971678130072078261E+01   1   1   1   1
 -1.91501428271686324756E+00   1   1   2   1
  4.38796949990802698238E+00   1   1   2   2

#!/bin/bash

# $1 : FCIDUMP file to convert from "new format" to "old format"

if [ ${#} -ne 1 ]
then
  echo "Syntaxis: fcidump_new2old FCIDUMPFILE" 1>$2
  exit 1
fi

if egrep '&FCI ([a-zA-Z2 ]*=[0-9 ]*,){2,}' ${1} > /dev/null
then
  echo "The provided file is already in old FCIDUMP format." 1>&2
  exit 2
fi

sed '
1,20 {
   :a; N; $!ba
   s/(=[^,]*,)n/1 /g
   s/(&FCI)n/1 /
   s/ORBSYM/n&/g
   s/&END/ISYM=1,n//
}' -i "${1}"

exit 0

script.sh: line 24: 406089 Killed                  sed '
1,20 {
   :a; N; $!ba
   s/(=[^,]*,)n/1 /g
   s/(&FCI)n/1 /
   s/ORBSYM/n&/g
   s/&END/ISYM=1,n//
}' -i "${1}"