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===== Packet Radio Shell Scripting ('PRSS') =====
Packet radio shell scripting ((c) dl3sjb) can be used to implement automated operations on the packet radio network using the well-known UNIX scripting language. 

Shell scripting involves chaining several UNIX commands together to accomplish a task. For example, you might login into the packet radio node, perform several commands and then use the output (i.e. 'find dl3sjb' => 'dl3sjb found on db0sao') to react interactively. I'll show you how to do this below. This is not a shell programming HOW-TO. We assume you are into it. If not, [[http://steve-parker.org/sh/sh.shtml]] (ENGLISH) -OR- [[http://de.wikibooks.org/wiki/Linux-Kompendium:_Shellprogrammierung]] (DEUTSCH) may be a good starting point.

Preparing LINUX:

First we need to define a 'deamon' that connects the LINUX shell with XNET on application level. The methodology behind this is pretty basic:
  - Create a 'FIFO' using the 'mkfifo' command - A "FIFO" is a special file type that permits independent processes to communicate. 
  - One process opens the FIFO file for writing, and another for reading, after which data can flow as with the usual anonymous pipe in shells.
  - The reading process is 'call', while the writing process is the UNIX shell script.
  - The output of 'call' is pushed into a log file from which the same UNIX shell script reads in order to process the packet radio data.

Let's get it on. The line starting with 'call' contains the most important point: we connect d1mmy (local XNET), write all data into '/tmp/ax25.log', read from '/tmp/pipe1' and write all 'errors' to the null device (waste bucket).
<code>
root@OpenWrt:~# cd /tmp
root@OpenWrt:~# mkfifo pipe1
root@OpenWrt:~# ls -al pipe1
prw-r--r--    1 root     root            0 Apr  3 02:33 pipe1
root@OpenWrt:~# call -r ax0 d1mmy 1>/tmp/ax25.log 0</tmp/pipe1 2>/dev/null &
root@OpenWrt:~# ps | grep "call"
  500 root            Z   [call]
root@OpenWrt:~# echo -e "\r" >pipe1
root@OpenWrt:~# ps | grep "call"
  524 root        420 R   call -r ax0 d1mmy
root@OpenWrt:~# cat ax25.log
GW4PTS AX.25 Connect v1.11
(X)NET/LINUX/MIPSel V1.39
=>

root@OpenWrt:~#
</code>

Once the packet radio connection is established, 'call' permanently polls 'pipe1' for new inputs. In order to avoid cpu time interferences with other processes , we need to decrease 'call's' process priority using 'renice'. This little program alters the priority of any process and sets the priority to any value in the range PRIO_MIN (-20) to PRIO_MAX.  Useful priorities are: 20 (the affected processes will run only when nothing else in the system wants to), 0 (the ``base'' scheduling priority), anything negative (to make things go very fast).

SYNOPSIS:  **renice** <priority> <pid>

<code>
root@OpenWrt:~#renice 20 524
524: old priority 0, new priority 20
root@db0sao_home0:/usr/local/icqcq#
root@OpenWrt:~#
</code>
Note: 'renice' is not part of the standard image, please download it from here {{projects:openwrt:renice.gz|}}, gunzip it and place it under /bin. It is not mandatory to use 'renice', but recommended. 'Reince' may become a part of future images.
<code>
root@OpenWrt:~# cd /bin
root@OpenWrt:/bin# ls -al renice
-rwxr--r--    1 root     root         8000 Nov 11 21:14 renice
root@OpenWrt:/bin#
</code>



In the following, the basic communication procedure is explained. Bottom line: 'echo' what you would type in a packet radio terminal into 'pipe1' (in binary mode => 'echo -e') and read what you would see in the terminal window from '/tmp/ax25.log' using 'cat'.

<code>
root@OpenWrt:~# call -r ax0 d1mmy 1>/tmp/ax25.log 0</tmp/pipe1 2>/dev/null &
root@OpenWrt:~# echo -e "\r" >/tmp/pipe1
root@OpenWrt:~# cat /tmp/ax25.log
GW4PTS AX.25 Connect v1.11
*** Connected to d1mmy
Rawmode
(X)NET/LINUX/MIPSel V1.39
=>
root@OpenWrt:~# echo -e "find dg8ngn" >/tmp/pipe1
root@OpenWrt:~# cat /tmp/ax25.log
=>
*** route: found DG8NGN via DB0FHN
root@OpenWrt:~#
</code>

If you now were to throw all commands into a shell script, just execute this script kin order to process the data automatically.

Example: this script connects the local XNET, executes the "find" command and then waits for either a successful find - OR - stops after 10 seconds. At the end it disconnects from the local XNET.
<code>
root@OpenWrt:~# vi /tmp/ax_connect_and_find.sh
#!/bin/sh
# by DL3SJB 
# What does it do?
# It connects via ax25d to local XNET and attempts to find a user using the "find" command. 
# If found, it sends a message to the user telling him that his buddy has been found.

call -r ax0 d1mmy 1>/tmp/ax25.log 0</tmp/pipe1 2>/dev/null &
sleep 1
echo -e "find $1" >/tmp/pipe1
grep "*** route" /tmp/ax25.log >/tmp/ax25found.log
while test -f /tmp/ax25found.log
         do
                if [ "`cat /tmp/ax25found.log|head -c9`" = "*** route" ]
                    then
                          echo -e "`cat /tmp/ax25found.log`"
                          rm -rf /tmp/ax25found.log
                    else
                          grep "*** route" /tmp/ax25.log >/tmp/ax25found.log
                          let i=$i+1
                          sleep 1
                          if [ $i -eq 10 ]
                                     then
                                           i=0
                                           echo -e "*** not found."
                                           rm -rf /tmp/ax25found.log
                                      fi
                          fi
done
echo -e "q" >pipe1

root@OpenWrt:~# chmod 755 /tmp/ax_connect_and_find.sh
root@OpenWrt:~# /tmp/ax_connect_and_find.sh dg8ngn
*** route: found DG8NGN via DB0FHN
root@OpenWrt:~# /tmp/ax_connect_and_find.sh test
*** not found.
root@OpenWrt:~# 
</code>
Note: Whenever you end the packet radio connection with 'echo -e "q" >pipe1 ', the 'call' program no longer runs in the background. It will be ended. So you need to restart 'call' whenever you intend to establish another connection. 

Conclusion: any type of shell script can use all packet radio resources using the above-described methodology. Various application are possible, such as "ICQ for packet radio" - OR - automatic "message of the day" publication in the node's connect text, etc.  The only down-side of this is that 'call' polls the FIFO. This is not the most efficient way of operation. On the other hand, the setup is working on any LINUX and does not require special software (other than 'renice' if you intend to ensure free cpu time for other time critical processes on your OPENWRT device). PRSS is not limited to OPENWRT.

Have fun.

Jens, DL3SJB, IPRT, DARC P42, April 2008

<code>
root@DB0SAO_1:~# dmesg 
usb 1-2: new full speed USB device using uhci_hcd and address 8
usb 1-2: configuration #1 chosen from 1 choice
pl2303 1-2:1.0: pl2303 converter detected
usb 1-2: pl2303 converter now attached to ttyUSB0
root@DB0SAO_1:~#
</code>

<code>
root@DB0SAO_1:/usr/local/xnet# cat AUTOEXEC.NET
attach SDEV0 SRPM 0 1 38400 /dev/ttyUSB0

</code>

<code>
* (1) CONNECTED to 0:DB0SAO via DL3SJB *
(X)NET/LINUX/MIPSel V1.39
=>p

po name            interface        baud    txd per w dup dam duo con   bit/s

 0 DB0LEL          0 SDEV0 SRPM     19200tr  55 255 7  1   0   0   7    4367

=>
</code>

<code>
BusyBox v1.4.2 (2008-02-28 05:09:35 CET) Built-in shell (ash)
Enter 'help' for a list of built-in commands.

  _______                     ________        __
 |       |.-----.-----.-----.|  |  |  |.----.|  |_
 |   -   ||  _  |  -__|     ||  |  |  ||   _||   _|
 |_______||   __|_____|__|__||________||__|  |____|
          |__| W I R E L E S S   F R E E D O M
 KAMIKAZE (7.09) -----------------------------------
  * 10 oz Vodka       Shake well with ice and strain
  * 10 oz Triple sec  mixture into 10 shot glasses.
  * 10 oz lime juice  Salute!
 ---------------------------------------------------
root@DB0SAO_1:~#

root@DB0SAO_1:~# call -r ax0 db0sao
GW4PTS AX.25 Connect v1.11
(X)NET/LINUX/MIPSel V1.39

18.02.09 09:06:30 DL3SJB-8 de DB0SAO :>l

Link to       dst  Q/T    rtt    tx connect   tx   rx   txq/rxq  rr+%  bit/s

 3:DB0LEL      17 F   1   1/1     0 45d 23h  682K 684K  100/100   0.1   1221
 5:DB0PRT       3 F  15   5/6     0  3d 57m  9.7K 9.7K   99/99    1.4    722
 
18.02.09 09:06:32 DL3SJB-8 de DB0SAO :>

root@DB0SAO_1:~#

</code>


<code>
#!/bin/sh
mkfifo pipe1
call -r -s dl3sjb-1 ax0 db0sao dl3sjb 1>./logfile.txt 0<pipe1 2>/dev/null &
echo -e "~0" >pipe1
echo -e "l" >pipe1
echo -e "q" >pipe1
sleep 10
echo "`grep "DB0LEL" logfile`"
exit

 3:DB0LEL      17 F   1   1/1     0 45d 23h  682K 684K  100/100   0.1   1221
</code>

<code>
root@OpenWrt:/mnt/harddisk/wrt54gs/icqcq.new# ./ax_icq_users
-------------------------------------
System: initating icq session on
        Sat Feb 21 09:59:43 CET 2009.

user: dk7td     buddies:
                          *** route: found DL8SDL-8 via DB0SAO
                          *** dl3sjb-1 not found.
                          *** route: found DB0XHI via DB0PRT

root@OpenWrt:/mnt/harddisk/wrt54gs/icqcq.new#

</code>

<code> 
7:fm ICQCQ to DB0SAO via DL3SJB ctl SABM+
7:fm DB0SAO to ICQCQ via DL3SJB* ctl UA-
7:fm ICQCQ to DB0SAO via DL3SJB ctl I00^ pid F0 [11]
f dl8sdl-8

7:fm DB0SAO to ICQCQ via DL3SJB* ctl I10^ pid F0 [54]
(X)NET/TNC3 V1.39
28.02.09 10:02:32 ICQCQ de DB0SAO :>
7:fm DB0SAO to ICQCQ via DL3SJB* ctl I11^ pid F0 [37]

28.02.09 10:02:32 ICQCQ de DB0SAO :>
7:fm DB0SAO to ICQCQ via DL3SJB* ctl RR1+
7:fm ICQCQ to DB0SAO via DL3SJB ctl RR2-
7:fm DB0SAO to ICQCQ via DL3SJB* ctl I12^ pid F0 [75]

*** route: found DL8SDL-8 via DB0SAO

28.02.09 10:02:32 ICQCQ de DB0SAO :>
7:fm DB0SAO to ICQCQ via DL3SJB* ctl RR1+
7:fm ICQCQ to DB0SAO via DL3SJB ctl RR3-
7:fm ICQCQ to DB0SAO via DL3SJB ctl DISC+
7:fm DB0SAO to ICQCQ via DL3SJB* ctl UA-
</code>

<code>
root@OpenWrt:/usr/local/xnet# cat aprs.sh
#!/bin/sh
mkfifo pipe 2>/dev/null

call -r -s dl3sjb-7 ax0 db0fhn-5 dl3sjb db0sao igate 1>blubber 0<pipe 2>/dev/nul                                                                                                                               l &
echo -e "\r" >pipe
echo -e "~0" >pipe
sleep 12


a="`cat blubber|tail -c 80|grep "*** Disconnected" -`"
if [ "$a" != "" ]
  then exit
      fi

a="`grep "Port full" blubber`"
if [ "$a" != "" ]
  then exit
    fi

echo -e "user DL3SJB-7 pass xxxxx vers UI-Glue 1.0 filter m/1" >pipe
sleep 4
#echo -e "DL3SJB>APU25N,TCPIP*:@212131z4836.12N/00917.93E_225/000g000t045r000p01                                                                                                                               0P000h88b10319" >pipe
echo -e "DL3SJB-6>APU25N,TCPIP*:`cat /tmp/APRSWX_FILE.txt`" >pipe
echo -e "\r" >pipe
echo "DL0SIN>APRSBW,TCPIP*:;OVP42/P26*000000!4839.24N\00856.42ER Jd. DO 19:00 OV                                                                                                                               -Stammtisch,Schlossstuben" >pipe
echo -e "\r" >pipe
pause 1

echo -e "~." >pipe
./ax_push "~." pipe
sleep 1
kill `ps | grep "call -r -s dl3sjb-7"|head -c5` 2>/dev/null
kill `ps | grep "ax_push" |head -c5` 2>/dev/null
#sleep 2
exit

#kill `ps |grep "call"|head -c5`
#kill `ps |grep "aprs.sh"|head -c5`
#exit
root@OpenWrt:/usr/local/xnet#

</code>

<code>

root@OpenWrt:/usr/local/xnet# (sleep 10; echo quit; sleep 2) | call -r ax0 db0sao 
GW4PTS AX.25 Connect v1.11
*** Connected to db0sao
Rawmode
(X)NET/TNC3 V1.39

18.02.09 10:21:19 DL3SJB-1 de DB0SAO :>
73!
*** Cleared
root@OpenWrt:/usr/local/xnet#

</code>
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