User`s manual
Table Of Contents
- 1. Introduction
- 2. Getting Started
- Powering on the W406-LX
- Connecting the W406-LX to a PC
- Configuring the Ethernet Interface
- USB Port for Expansion
- SD Socket for Storage Expansion
- Setting Up the Wireless Module
- Configuring the SIM Card
- Entering the PIN Code
- Verifying the SIM Card Status
- Enabling or Disabling the PIN Code Authentication
- Changing the PIN Code
- Unlocking the SIM Card
- Connecting to the Internet
- Reconnecting to the Internet
- Disconnecting from the Internet
- Detecting an Internet Connection Error
- Sending and Reading an SMS Message
- Deleting an SMS Message
- Test Program—Developing Hello.c
- 3. Managing Embedded Linux
- 4. Managing Communications
- 5. Development Tool Chains
- 6. Programmer’s Guide
- 7. Software Lock
- A. System Commands
W406-LX User’s Manual Managing Embedded Linux
3-9
Updating the Time Automatically
In this subsection, we show how to use a shell script to update the time automatically.
Example shell script to update the system time periodically
#!/bin/sh
ntpdate time.nist.gov # You can use the time server’s ip address or domain
# name directly. If you use domain name, you must
# enable the domain client on the system by updating
# /etc/resolv.conf file.
hwclock --systohc
sleep 100 # Updates every 100 seconds. The min. time is 100 seconds. Change
# 100 to a larger number to update RTC less often.
Save the shell script using any file name. E.g.,
fixtime
How to run the shell script automatically when the kernel boots up
Copy the example shell script
fixtime
to directory
/etc/init.d
, and then use
chmod 755 fixtime
to change the shell script mode. Next, use vi editor to edit the file
/etc/inittab
. Add the following line to the bottom of the file:
ntp : 2345 : respawn : /etc/init.d/fixtime
Use the command
#init q
to re-init the kernel.
Cron—Daemon to Execute Scheduled Commands
Start Cron from the file
/etc/rc.d/rc.local
. It will return immediately, so you don’t need to
start it with ‘&’ to run in the background.
The Cron daemon will search
/etc/cron.d/crontab
for crontab files.
Cron wakes up every minute, and checks each command to see if it should be run in the current
minute. Modify the file
/etc/cron.d/crontab
to set up your scheduled applications. Crontab
files have the following format:
min hour date month week user command
0-59 0-23 1-31 1-12 0-6 (0 is Sunday)
The following example demonstrates how to use Cron.
How to use cron to update the system time and RTC time every day at 8:00
STEP1: Write a shell script named fixtime.sh and save it to /home/.
#!/bin/sh
ntpdate time.nist.gov
hwclock --systohc
exit 0
STEP2: Change mode of fixtime.sh
#chmod 755 fixtime.sh
STEP3: Modify /etc/cron.d/crontab file to run fixtime.sh at 8:00 every day.
Add the following line to the end of the crontab:
* 8 * * * root /home/fixtime.sh
STEP4: Enable the cron daemon manually.
#/etc/init.d/cron start