PGPLOT at the ING

Gary F Mitchell
May 1999

This page gives a very basic example of using pgplot

Index

Recipe
Details on linking
Further information

Recipe

First create a simple fortran program with calls to PGPLOT functions and/or subroutines such as this example fortran code The PGPLOT library is described in a Starlink document - see "Further Information" below
```
Starlink User Note 15.7 
D L Terrett 
12 May 1997 
```
but we have PGPLOT installed in /opt/pgplot and not in /star. nevertheless the documentation of the library is the same.
Next compile it with special flags
```
gfm@cs1> f77 -L /opt/pgplot -lpgplot
```
The -L flag is followed by a directory name eg /opt/pgplot. The -l flag is followed by the name of a library file in that directory - but with the 3 characters "lib" removed from the name of the file. (see "Details on Linking" below if you're want to understand what these are).
run the program!
```
gfm@cs1> gfm1
```
The example program creates a PostScript file which can be examined by any PostScript interpreter eg the sdtimage application from CDE. Of course many more devices are supported by the PGPLOT drawing library eg X-window.

The -L flag is followed by a directory name eg /opt/pgplot. The -l flag is followed by the name of a library file - but with the 3 characters "lib" removed from the name of the file. It sounds complex but these options serve to inform the compiler that references to subroutines not in the source code can be resolved by looking at directory /opt/pgplot and search for files libpgplot*. If you or the compiler look at /opt/pgplot you will see

-rw-r--r--   1 root     other      79832 May 14 15:06 /opt/pgplot/libcpgplot.a
-rw-r--r--   1 root     other     776824 May 14 14:58 /opt/pgplot/libpgplot.a
-rwxr-xr-x   1 root     other     503364 May 14 14:58 /opt/pgplot/libpgplot.so

The file libcpgplot.a is for C programs. The file libpgplot.a is an archive of object files. You can examine it's contents using the ar command

gfm@cs1> ar -t /opt/pgplot/libpgplot.a
figdisp_comm.o
gidriv.o
grarea.o
grbpic.o
grchsz.o
...
...
vadriv.o
wddriv.o
x2driv.o
xwdriv.o

The file libpgplot.so is a shared object library. It has the same content as the archive file but in a different form.

When you link the program you either do a static link or a dynamic link.

static link: The compiler collects a copy of the required subroutine from the archive file libpgplot.a and builds it into your application and makes a big image.
dynamic link: The compiler checks that libpgplot.so has what you want and merely annotates the image it is building with an instruction to go get the remaining subroutines from the shared object library at run time.

The option static vs dynamic is controlled by a flag to the compiler such as -Bdynamic or -Bstatic or -dy -dn. The default is to attempt a dynamic link but resort to static if there is no shared obsject library file.

The recommendation of CFG is to accept the system default and have a dynamic link.

Further information

For more information on flags for the f77 compiler use the command
```
f77 -flags
```
For a really quick intro to flags for libraries use grep
```
f77 -flags | grep lib
```
For some web pages about the f77 compiler use the following reference in your browser
```
file:/opt/SUNWspro/DOC4.0/lib/locale/C/html_docs/index.html
```
PGPLOT --- Graphics Subroutine Library
("file:/star/docs/sun15.htx/sun15.html")

This page is available on-line at http://www.ing.iac.es/~cfg/notes/pub_notes/pgplot/

PGPLOT at the ING

Index

Recipe

Details on linking

Further information