.\" $Header$
.nr yr \n(yr+1900
.af mo 01
.af dy 01
.TH ncmpidiff 1 "PnetCDF 1.11.0" "Printed: \n(yr-\n(mo-\n(dy" "PnetCDF utilities"
.SH NAME
ncmpidiff \- compares two netCDF files in parallel
.SH SYNOPSIS
.ft B
.HP
mpiexec -n np ncmpidiff
.nh
\%[-b]
\%[-q]
\%[-h]
\%[-v \fIvar1,...\fP]
\%\fIfile1 file2\fP
.hy
.ft
.SH DESCRIPTION
\fBncmpidiff\fP runs in parallel on np number of MPI processes to compare the
contents of the two files and reports the difference to the standard output.

If neither argument -v nor -h is given besides the two file names, the entire
files are compared.

When comparing two files entirely, the difference between \fBncmpidiff\fP and the
Unix command \fBdiff\fP is that \fBncmpidiff\fP skips the gaps between variables. The
gaps may occur when the alignment feature is used to create a new file. This
alignment allows to allocate a larger space for the file header and align the
starting file offsets of fixed-size variables (see API \fBncmpi__enddef\fP and
\fBPnetCDF hints\fP). Oftentimes, the contents of gaps are non-zero arbitrary
bytes. Thus, two netCDF files (of same or different sizes) can be reported
identical by \fBncmpidiff\fP but not by \fBdiff\fP.

.SH OPTIONS
.IP "\fB-b\fP"
Verbose mode - print results (same or different) for all components (file,
header, or variables) in comparison
.IP "\fB-q\fP"
Quiet mode - print nothing on the command-line output. This also disables
verbose mode. When in quiet mode, users should check exit status. See below in
"EXIT STATUS".
.IP "\fB-h\fP"
Compare file header only
.IP "\fB-v\fP \fIvar1,...,varn\fP"
Compare only the given list of variables
.SH EXIT STATUS
An exit status of 0 means no differences were found, and 1 means some
differences were found.  Note on VMS-based system, the exit status values are
reversed.
.SH "SEE ALSO"
.LP
.BR ncmpidump (1),
.BR diff (1),
.BR pnetcdf (3)
.SH DATE
19 Dec 2018
.LP