Conversion between different data file formats

For AMBER

xyz -> inpcrd

  awk '{printf("%12.7f %11.7f %11.7f "), $1, $2, $3} {getline} {printf("%11.7f %11.7f %11.7f\n"), $1, $2, $3}' input.xyz > input.inpcrd

For AMBER and CHARMM

crd -> pdb

  tail +2 input.crd > tmp
  awk '{printf"%4s%7d %-4s%4s %s%5d%11.3f%8.3f%8.3f\n", "ATOM",$1,$4,$3,"A",$2,$5,$6,$7}' tmp > input.pdb
  rm tmp

pdb -> crd

  awk '{if ($1!="TER" && $1!="END") printf"%5d%5d%4s  %-4s%17.12f%17.12f%17.12f%6s  %-4d\n", $2,$5,$4,$3,$6,$7,$8,"NAME",$5}' input.pdb > tmp1
  wc -l tmp1 | awk '{print $1}'> tmp2
  cat tmp1 tmp2 > input.crd
  rm tmp1 tmp2

Notes:

1. Conversion between .crd and .pdb can be done by CHARMM- more info can be found on the page for converting between '.crd' and '.pdb'

2. The same thing can be done by VMD - both for AMBER and CHARMM files.

3. In AMBER package you can find useful program called ambpdb. It can convert many formats and binary output files as well as add some interesting information like hydrogen bonds or salt bridges.