Echo bar in $version = 'bar'

[FakeOutdoorsman]

I'm not a programmer at all, but I'm trying to write a bash script that will download a file, check it's md5sum, compare to the online md5sum and then continue. I am trying to figure this out myself so I can learn, but I am stuck at echoing a value from a file that contains a version number:

$version = 'bar'

The bar is often in the format of 1.2 or 1.2.5 for example. How do I echo just the bar? Simple stuff, but over my head so far.

[ibuclaw]

I'm not a programmer at all, but I'm trying to write a bash script that will download a file, check it's md5sum, compare to the online md5sum and then continue. I am trying to figure this out myself so I can learn, but I am stuck at echoing a value from a file that contains a version number:

$version = 'bar'

The bar is often in the format of 1.2 or 1.2.5 for example. How do I echo just the bar? Simple stuff, but over my head so far.

The version number is kept in a file? or is it hard-coded as a string?

If bar is an actual string, you should be doing it like this:

version='bar'

and then use $version to reference the value.

Regards
Iain

[FakeOutdoorsman]

Thanks for the reply. The version number is kept in a php file located in the archive that the script downloads, specifically wordpress/wp-includes/version.php. It's the Wordpress version number and an example can be seen here: version.php. Eventually, my script will download latest.tar.gz and then compare it's md5sum to the md5sum shown online for the corresponding version. Here is what I have so far:

#!/bin/bash
version="duh..."
md5sumlocal= `md5sum latest.tar.gz | cut -c1-32`
md5sumonline=`curl http://wordpress.org/wordpress-"$version".md5`

if [ -e "latest.tar.gz" ]; then
        rm -rf latest.tar.gz
fi

wget http://wordpress.org/latest.tar.gz

if [ "$md5sumlocal" != "$md5sumonline" ]; then
        echo
        echo "md5sum failed!"
        exit
fi

I can't figure out how to get the 2.8.5 from $wp_version = '2.8.5'; so I can apply it to the curl command.

Also, a few more questions. Should I be using != or -ne? What is the difference between ${foo} and "$foo"?

[eightmillion]

I can't figure out how to get the 2.8.5 from $wp_version = '2.8.5'; so I can apply it to the curl command.

How about something like this to get the version:

version=$(curl -s http://core.svn.wordpress.org/trunk/wp-includes/version.php | awk -F\' '/^\$wp_version/{print $2}') 

Also, a few more questions. Should I be using != or -ne?

!= is for comparing strings so it's what you should be using in this particular instance. -ne is for comparing integers.

What is the difference between ${foo} and "$foo"?

${foo} is used when you want to clearly delineate variables. Let's say that foo=123, and you want to echo the value of foo plus the word "bar". You might do something like "echo $foobar". Bash will interpret that as the variable foobar and either return the value of $foobar if it's set or nothing at all if it's not. "echo ${foo}bar" will actually echo 123bar. Note that if you use the braces syntax, you still have to quote a variable to maintain spaces. See this example:

$ foo="bar baz"
$ echo $foobar

$ echo ${foo}bar
bar bazbar
$ if [ ${foo} == "bar baz" ];then echo True; fi
bash: [: too many arguments
$ if [ "${foo}" == "bar baz" ];then echo True; fi
True


#Just to demonstrate different comparison operators:
$ if [ "${foo}" -eq "bar baz" ];then echo True; fi
bash: [: bar baz: integer expression expected 

[FakeOutdoorsman]

How about something like this to get the version:

version=$(curl -s http://core.svn.wordpress.org/trunk/wp-includes/version.php | awk -F\' '/^\$wp_version/{print $2}') 

This works great. I thought awk was the tool to use, but I just could not figure it out. I just modified it slightly to get the version from the local version.php instead:

version=$(awk -F\' '/^\$wp_version/{print $2}' wordpress/wp-includes/version.php) 

!= is for comparing strings so it's what you should be using in this particular instance. -ne is for comparing integers.

${foo} is used when you want to clearly delineate variables. Let's say that foo=123, and you want to echo the value of foo plus the word "bar". You might do something like "echo $foobar". Bash will interpret that as the variable foobar and either return the value of $foobar if it's set or nothing at all if it's not. "echo ${foo}bar" will actually echo 123bar. Note that if you use the braces syntax, you still have to quote a variable to maintain spaces. See this example:

$ foo="bar baz"
$ echo $foobar

$ echo ${foo}bar
bar bazbar
$ if [ ${foo} == "bar baz" ];then echo True; fi
bash: [: too many arguments
$ if [ "${foo}" == "bar baz" ];then echo True; fi
True


#Just to demonstrate different comparison operators:
$ if [ "${foo}" -eq "bar baz" ];then echo True; fi
bash: [: bar baz: integer expression expected 

Thanks for the excellent examples describing how this works. It's very helpful.