[SOLVED] Scripting Question

[Dave-Oregon]

Hi,

I have a script I am running:

#!/bin/sh
# Network status.
# Pass name of network interface, such as eth0, as $1

interface=$1 #Save value, because we overright $1

stats=`netstat -i | grep $interface | tail -1`

set $stats
echo $4
echo $8

echo `uptime`
echo `hostname`

I want to write a value to a file on disk, then get it later... What command, or commands will allow me to write a value to to a file, and what command or commands will allow me to get it back? Are variables typed in this environment? Looking to save off the if byte value to a file, then get it later then sub it from teh current then assign to a varib and graph in mrtg...

Thanks,
Dave

[Cabhan]

Variables in both the Bourne shell (sh) and Bash are untyped. So there's that answer.

It is possible that you need the value to be stored in a file for other reasons, but it seems silly to store a value in a file and then retrieve it. You can always simply assign it to another variable if you need to reuse a particular one.

In any event, writing and reading from files in Bash is fairly simple:

echo "hello" > file # this creates file "file" if it doesn't exist, and removes all the content of "file" if it does exist.  It then writes "hello" to the file.
echo "hello" >> file # this creates file "file" if it doesn't exist, and appends "hello" to the end of the file
read variable < file # this reads the first line of file "file" into the variable $variable

Does this make sense?

[Dave-Oregon]

Hi,

Thanks for teh answer, I'll mess with this later today! I need to keep the value between runs of the script. What I am doing is to save off the current byte count, then on next invocation recall it, subtract it from the current byte count, and then have the number of bytes that moved between runs... If there is a better way, I am all ears!!!

Thanks again!!!
Dave

[Dave-Oregon]

Thanks again, here is the finished script...
#!/bin/sh
# Network status.
# Pass name of network interface, such as eth0, as $1

#Preload some items for use
#grab old value from file named net2mrtg.save and give it a name
read oldbytein < net2mrtg.data0
read oldbyteout < net2mrtg.data1

#Give Command Tail $1 a name
interface=$1

#Generate a string to fetch data from
stats=`netstat -i | grep $interface | tail -1`

#Use that string
set $stats

#save current byte counts to files
echo $4 > net2mrtg.data0
echo $8 > net2mrtg.data1

#Move current value into a variable for use later
newbytein=$4
newbyteout=$8

#Do the math...
usedbytein=`expr $newbytein - $oldbytein`
usedbyteout=`expr $newbyteout - $oldbyteout`
#Feed to MRTG
echo $usedbytein
echo $usedbyteout
echo `uptime`
echo `hostname`

Thanks again for the help folks!!!

Dave