Hints to Build-from-Source:

Generic Build Hints:
• The two NCO build mechanisms: NCO has two build mechanisms: (1) GNU configure and (2)  a custom Makefile (nco/bld/Makefile) designed for hand-editing. Try the traditional GNU configure method first, i.e., ./configure;make;make check;make install. This method involves no hand-editing of makefiles, but trouble-free builds with it are less common than we would like. The file nco/configure.eg contains a table which describes the success you can expect building NCO with the configure mechanism. If the simple configure recipe above does not work, savvy users may find it straightforward to modify and use the following, more advanced configure recipe:

  # gcc/g++ Sysadmins use/modify this to install/update NCO in /usr/local, based on netCDF4 also in /usr/local (works on givre 20100727):
  export GNU_TRP=`~/nco/autobld/config.guess`
  cd ~/nco;/bin/rm -f *.${GNU_TRP}.foo;make distclean
  CPPFLAGS='-DHAVE_NETCDF4_H -I/usr/local/include' LDFLAGS='-L/usr/local/lib' ./configure --prefix='/usr/local' --enable-ncap2 --enable-netcdf4 > nco.configure.${GNU_TRP}.foo 2>&1
  /bin/cp -f config.log nco.config.log.${GNU_TRP}.foo
  /bin/cp -f libtool nco.libtool.${GNU_TRP}.foo
  make clean;make > nco.make.${GNU_TRP}.foo 2>&1
  make check >> nco.make.${GNU_TRP}.foo 2>&1
  sudo make install >> nco.make.${GNU_TRP}.foo 2>&1
  

  This is the recipe that the developers use to test configure on their machines. Please contribute patches required to get the configure mechanism working properly for NCO on your platform. The regressions archive contains gory details of successful (and failed) builds for many platforms. Plaform-specific build hints (CentOS, Mac OS X, RHEL, Solaris) are listed below.
  All platforms continue to work fine with the nco/bld/Makefile method:

  export MY_BIN_DIR='/home/username/bin' # Executables installed here
  export MY_OBJ_DIR='/home/username/obj' # Object files placed here
  export MY_LIB_DIR='/home/username/lib' # Libraries built here
  mkdir -p ${MY_BIN_DIR} ${MY_OBJ_DIR} ${MY_LIB_DIR}
  cd ~/nco/bld
  make dir
  make all
  make ncap2
  make test
  

  Disadvantages are that nco/bld/Makefile (1) Usually requires editing to fix your platforms paths; (2) Does not support shared libraries; and (3) Requires a degree from Hogwarts to understand.
• Duplicate symbols errors: When building NCO with the netCDF4 library and headers, some compilers emit errors due to duplicate symbol definitions. This arises because of the complexity of the build system. Essentially, NCO has to define some netCDF API prototypes itself to handle the corner case where the netCDF4 distribution is used to build netCDF3 libraries. We have tried to address this issue using autoconf/configure but it is beyond our abilities. The fix is to manually tell NCO that the netCDF4 header file netcdf.h is in fact being used so that NCO should not attempt to define these prototypes. Do this, e.g., with CPPFLAGS='-DHAVE_NETCDF4_H' or USR_TKN='-DHAVE_NETCDF4_H' if you use configure.
• Build Chain Version Incompatibilities: NCO requires GNU make version ≥ 3.78.1 to support target-specific variable values in bld/Makefile. NCO most often fails to build because ncap fails to build. Two of the most common reasons that ncap fails to build are (1) GNU bison is out-of-date (upgrade bison) and (2) --enable-optimize-* is specified to configure (do not specify it).
  
• C99-compliance & old compilers: NCO versions ≥ 2.9.8 require the compiler to support the 1999 ISO C-Standard called C99. NCO takes advantage of two C99 features, restricted pointers and designated initializers. To build NCO versions ≥ 2.9.8 without a C99-compliant compiler, simply undefine the restrict type qualifier before compiling NCO. Do this, e.g., with CPPFLAGS='-Drestrict='. More details on C99 compatibility are in the header file nco/src/nco/nco.h.
  
• Old netCDF libraries: NCO versions ≥ 3.0.0 require netCDF versions ≥ 3.6 to take advantage of the new 64-bit offset file type. The library and include directories (e.g., /usr/lib and /usr/include, respectively) for netCDF version ≥ 3.6 must be on the path searched by the compiler, and must precede the locations of any older netCDF installations. To build NCO versions ≥ 3.0.0 with older netCDF versions < 3.6, simply define the pre-processor token NC_64BIT_OFFSET to 0 before compiling NCO. Do this, e.g., with CPPFLAGS='-DNC_64BIT_OFFSET=0' or USR_TKN='-DNC_64BIT_OFFSET=0' if you use configure or bld/Makefile, respectively. Users attempting to build NCO with OPeNDAP versions ≤ 3.6.x may need this workaround because OPeNDAP did not fully support netCDF version 3.6.x functionality until OPeNDAP versions ≥ 3.7.0. (The indicator for this problem is a build error like "nco_fl_utl.c", line 30.20: 1506-045 (S) Undeclared identifier NC_64BIT_OFFSET.) All modern NCO versions require netCDF versions ≥ 3.5.0 to support nc_type NC_NAT in NCO source code. NCO versions 3.9.0 and greater (May, 2007) require netCDF versions ≥ 3.6.0 to resolve the nc_inq_format() function.
• ncap build hints: ncap is a sophisticated and somewhat fragile program. ncap requires flex to build correctly. AT&T lex will not work because it does not understand EOF rules used in ncap_lex.l. bison version 1.29 (the default version on early Mac OS X) is buggy and does not parse ncap_yacc.y correctly; previous and later bison's work correctly. bison version 1.25 will not build ncap on Solaris. Please upgrade bison to the latest version (e.g., 1.875+) before reporting ncap build problems. If ncap keeps you from building NCO, and you do not need ncap, configure with --disable-ncap (and know that ncwa will fail to build as a result).
• Build Hints with GSL:
  NCO versions 3.9.6— support automatic building and linking for GSL versions 1.4—. Earlier GSL versions are not supported.
  
• Build Hints with DAP:
  NCO versions 3.9.9— support automatic building and linking for DAP supplied from libnetcdf versions 4.1-beta1 and beyond
  NCO versions 3.1.3— support automatic building and linking for OPeNDAP versions 3.6.x and GCC versions 4.0+.
  NCO versions 3.0.1—3.1.2 support automatic building and linking for OPeNDAP versions 3.5.x and GCC versions 3.4+.
  NCO versions 2.8.5—3.0.0 support automatic building and linking for OPeNDAP versions 3.4.x and GCC versions 3.3+.
  NCO versions ?.?.?—2.8.4 support automatic building and linking for DODS versions 3.2.x and GCC versions 3.2+.
  No other version combinations are supported.
• libnco_c++ build hints: libnco_c++ requires a good C++ compiler to build correctly. Few people need libnco_c++, so the workaround is not to build it. This is done by configuring with --disable-nco_cplusplus.

Platform-Specific Build Hints:
• AIX build hints: NCO versions 2.8.7+ do not build with autotools under AIX when --enable-optimize-* is selected. The workaround is to not use --enable-optimize-*. NCO versions 2.9.7+ do not build shared libraries with AIX xlc compilers because of silly AIX library dependencies activated by OpenMP directives. The workaround is to configure with --disable-shared.
• IRIX build hints: The most common problem with building on SGI IRIX is an out-of-date toolchain.
• Mac OS X build hints: Mac OS X users report success building NCO without patches so long as they (1) Install the latest version of bison, (2) Disable shared libraries and (3) Disable extended regular expressions. This is done with ./configure --disable-regex --disable-shared Building NCO with shared libraries on Mac OS X on may be possible. To try, first re-build and re-install the netCDF library using CFLAGS=-fno-common. Apparently netCDF, unlike most codes, does not set this automatically. Then build NCO normally. Mac OS X ships with a broken version of the POSIX cut utility which causes many NCO regression tests to appear to fail. In fact the NCO commands succeed, but the cut output fails. The workaround is not to heed the regression tests, or to install a working cut, e.g., from the GNU coreutils package.
• RHEL build hints: Scripts for generating executables for recent (4.0.x, ~2011) versions of NCO for RedHat Enterprise Linux 5 (RHEL5) and CentOS5 platforms are described here. Older information on building x86_64 RPMs is available here.
• Solaris build hints: All recent NCO versions build with autotools on Solaris 2.7—2.9. The most common problem with building on Solaris with cc/CC is that bison may be out-of-date. Install an up-to-date bison (e.g., 1.875+). Solaris 2.10, i.e., Solaris10, had the audacity to change the prototype of the ctime_r() function and so does not build NCO 3.0.1. The fix is to upgrade to the current NCO version.
• SX build hints: NEC SX does not understand the S_ISLNK macro, preferring instead the (non-POSIX) S_IFLNK macro. This macro appears in the file nco_fl_utl.c. The patch I wrote for this may be broken. Will someone with NEC SX please send us a working patch?
• Windows build hints: Building on Microsoft Windows is possible with Cygwin. The resulting executables will behave normally on local files, but will not have some (most?) of NCO's network functionality (e.g., scp, OPeNDAP). See the User's Guide for more details.