markomedia - web development

At Learnosity I’ve spent last 2 days scripting virtual server deployment on Amazon cloud. For my reference, these are some useful commands I had to use to get the job done.
1. Hash “Hello World” string using SHA256 algorithm

echo -n "Hello World" | shasum -a 256

You can also hash a file

shasum -a 256 myfile.ext

2. Display server IP address by stripping out all other network information, including the local 127.0.0.1 IP

ifconfig  | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}'

3. Read out first 64 characters from a long string

${mystring:0:64}

4. While loop with 10 iterations

i=0;
while [ $i -lt 10 ]
do
    echo $i
    i=$[$i+1]
done

5. Replace contents of a file. For example search for string1, replace with string2 in myfile.txt

sed -e "s/string1/string2/g" myfile.txt > myfile.txt_temp
mv myfile.txt_temp myfile.txt

6. Display number of CPU processors on Linux
The command simply pulls out all instances of the word ‘processor’ from /proc/cpuinfo and returns the word count of it.

cat /proc/cpuinfo | grep processor | wc -l

Marko

I recently changed my ISP from Optus to TPG and when I tried to start my local apache instance and I got this error

httpd: apr_sockaddr_info_get() failed for 192-168-1-107.tpgi.com.au
httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName

That gave me a hint that my local hostname had changed. I reset it back to what it was originally like this:

sudo hostname myoldhostname.local

Restarted apache and it was smooth sailing again.

Marko