How to use "-o ..." flag as a delimiter to separate output file from input files in a "babel" command?

The "-o ..." flag is optional, since "babel" command can implicitly determine the output data format from the file extension of output file name.

However, it is important to use the "-o ..." flag as a delimiter to separate output file from input files. For example, following "babel" commands show you how "-o ..." can be used to write good "babel" command lines:

# good command line: all.sdf, delimited by "-o ...", is the output 
babel mol-20001.sdf mol-20002.sdf mol-20003.sdf -o sdf all.sdf

# poor command line: all.sdf, the last one in the list, is the output
babel mol-20001.sdf mol-20002.sdf mol-20003.sdf all.sdf

# good command line: "stdout", delimited by "-o ...", is the output 
babel mol-20001.sdf mol-20002.sdf mol-20003.sdf -o sdf

# bad command line: mol-20003.sdf is the output, original data is replaced
babel mol-20001.sdf mol-20002.sdf mol-20003.sdf

⇒ "babel" Command - From STDIN To STDOUT

⇐ "babel" Command - Output Data Destination and Format

⇑ Understanding "babel" Command Line Syntax

⇑⇑ Open Babel Tutorials