ncap arithmetically processes a netCDF file. The processing instructions are contained either in the NCO script file fl.nco or in a sequence of command line arguments. The options -s (or long options --spt or --script) are used for in-line scripts and -S (or long options --fl_spt or --script-file) are used to provide the filename where (usually multiple) scripting commands are pre-stored. ncap was written to perform arbitrary albebraic transformations of data and archive the results as easily as possible. Missing values are treated correctly. The results of the algebraic manipulations are called derived fields.

Unlike the other operators, ncap does not accept a list of variables to be operated on as an argument to -v. Rather, the -v switch takes no arguments and indicates that ncap should output only user-defined variables. ncap does not accept or understand the -x switch.

Compute the square of variable T

ncap -s "T2=T*T" in.nc out.nc

If the info and NCO programs are properly installed at your site, the command

info nco

should give you access to the complete manual, except for the TeX-intensive portions.