File: gawk.info,  Node: Using Internal File Ops,  Prev: Internal File Ops,  Up: Extension Example

17.6.3 Integrating the Extensions
---------------------------------

Now that the code is written, it must be possible to add it at runtime
to the running 'gawk' interpreter.  First, the code must be compiled.
Assuming that the functions are in a file named 'filefuncs.c', and IDIR
is the location of the 'gawkapi.h' header file, the following steps(1)
create a GNU/Linux shared library:

     $ gcc -fPIC -shared -DHAVE_CONFIG_H -c -O -g -IIDIR filefuncs.c
     $ gcc -o filefuncs.so -shared filefuncs.o

   Once the library exists, it is loaded by using the '@load' keyword:

     # file testff.awk
     @load "filefuncs"

     BEGIN {
         "pwd" | getline curdir  # save current directory
         close("pwd")

         chdir("/tmp")
         system("pwd")   # test it
         chdir(curdir)   # go back

         print "Info for testff.awk"
         ret = stat("testff.awk", data)
         print "ret =", ret
         for (i in data)
             printf "data[\"%s\"] = %s\n", i, data[i]
         print "testff.awk modified:",
             strftime("%m %d %Y %H:%M:%S", data["mtime"])

         print "\nInfo for JUNK"
         ret = stat("JUNK", data)
         print "ret =", ret
         for (i in data)
             printf "data[\"%s\"] = %s\n", i, data[i]
         print "JUNK modified:", strftime("%m %d %Y %H:%M:%S", data["mtime"])
     }

   The 'AWKLIBPATH' environment variable tells 'gawk' where to find
extensions (*note Finding Extensions::).  We set it to the current
directory and run the program:

     $ AWKLIBPATH=$PWD gawk -f testff.awk
     -| /tmp
     -| Info for testff.awk
     -| ret = 0
     -| data["blksize"] = 4096
     -| data["devbsize"] = 512
     -| data["mtime"] = 1412004710
     -| data["mode"] = 33204
     -| data["type"] = file
     -| data["dev"] = 2053
     -| data["gid"] = 1000
     -| data["ino"] = 10358899
     -| data["ctime"] = 1412004710
     -| data["blocks"] = 8
     -| data["nlink"] = 1
     -| data["name"] = testff.awk
     -| data["atime"] = 1412004716
     -| data["pmode"] = -rw-rw-r--
     -| data["size"] = 666
     -| data["uid"] = 1000
     -| testff.awk modified: 09 29 2014 18:31:50
     -|
     -| Info for JUNK
     -| ret = -1
     -| JUNK modified: 01 01 1970 02:00:00

   ---------- Footnotes ----------

   (1) In practice, you would probably want to use the GNU Autotools
(Automake, Autoconf, Libtool, and 'gettext') to configure and build your
libraries.  Instructions for doing so are beyond the scope of this Info
file.  *Note gawkextlib:: for Internet links to the tools.